GISENYI, RWANDA (NYTIMES) - They are sometimes tucked into bras, hidden in underwear or coiled tightly around a smuggler's arms.
They're not narcotics or even the illegally mined gold and diamonds that frequently make it across the border into Rwanda. But they are, at least in the eyes of Mr Egide Mberabagabo, a watchful border guard, every bit as nefarious.
The offending contraband? Plastic bags.
"They're as bad as drugs," said Mr Mberabagabo, one of a dozen border officials whose job is to catch smugglers and dispose of the illicit plastic he finds.
Here in Rwanda, it is illegal to import, produce, use or sell plastic bags and plastic packaging except within specific industries such as hospitals and pharmaceuticals. The nation is one of more than 40 around the world that have banned, restricted or taxed the use of plastic bags, including China, France and Italy.
But Rwanda's approach is on another level. Traffickers caught carrying illegal plastic are liable to be fined, jailed or forced to make public confessions.
Smugglers can receive up to six months in jail. The executives of companies that keep or make illegal plastic bags can be imprisoned for up to a year, officials say. Stores have been shut down and fined for wrapping bread in cellophane, their owners required to sign apology letters - all as part of the nation's environmental clean-up.
Plastic bags, which take hundreds of years to degrade, are a major global issue, blamed for clogging oceans and killing marine life. Last month, Kenya put in place a rule that will punish anyone making, selling or importing plastic bags with as much as four years in jail or a US$19,000 (S$25,940) fine.
In Rwanda, the authorities say the bags contribute to flooding and prevent crops from growing because rainwater cannot penetrate the soil when it is littered with plastic.
The nation's zero-tolerance policy toward plastic bags appears to be paying off: Streets in the capital, Kigali, and elsewhere across this hilly, densely populated country are virtually spotless. Men and women are regularly seen on the sides of roads sweeping up rubbish, and citizens are required once a month to partake in a giant neighbourhood cleaning effort, including the president.
Plastic-bag vigilantes are everywhere, from airports to villages, and these informants tip off the authorities about suspected sales or use of plastic.
One recent afternoon, Mr Mberabagabo, the border official, surveyed the crossing point with the Democratic Republic of Congo, where thousands of people, as well as goods and animals, flowed back and forth, punctuated by shouts, cries and animal grunts.
Plastic tubs filled with onions, eggplants, carrots, plantains and cassava bobbed above the heads of women who marched purposefully, with places to go, money to make and mouths to feed. And somewhere among them, often tucked in the women's undergarments, he said, were hundreds of plastic bags.
"The most extreme cases are the ladies," he said, before adding bashfully: "It's not very easy to search them."
An immigration official working alongside Mr Mberabagabo showed footage on his cellphone of a middle-aged woman who had been caught transporting plastic bags wrapped around her arms. In the clip, she sobbed and apologised, shielding her eyes from the camera as if she were a drug dealer exposed in a sting operation on television.
The official, expressing a mix of awe and frustration at the lengths to which smugglers will go, showed another video clip of a wheelchair that had a false bottom concealing bundles of tightly packed plastic bags. He puffed with pride while recounting how he discovered the deceit.
Nearby, a tall plastic bin was filled to the brim with plastic bags, from the large supermarket kind to the small, translucent types used to pack sandwiches. A big banner read: "Use environmentally friendly bags" as officials searched luggage and patted down entrants.
Rwanda is probably Africa's cleanest nation and among the most pristine in the world. Though at least 15 African countries have enacted some sort of ban, many still have plastic bags littered on roads, stuck in drain pipes or caught in trees. Cattle die eating the bags because they obstruct digestion. In informal settlements in places like Kenya, plastic bags are sometimes used as "flying toilets" containing human waste.
There are, of course, many environmental threats on the continent, including poaching, water pollution and deforestation. Some countries are trying to tackle them, like Gabon, where the president has fashioned himself as an environmentally conscious leader. But many nations lack the resources or political will. Congo bans plastic bags, in theory, but there is little to suggest the ban is enforced.
Kinshasa, Congo's capital, has so much trash, most of it contained in plastic bags, that the city's residents have nicknamed the city "poubelle", or "garbage can." In Goma, a Congolese city just across the border with Rwanda, plastic litter is everywhere, made even more visible because the earth there is made of black, volcanic rock. Clumps of coloured plastic poke out of the ground like weird vegetation.
"Rwanda is very clean; here in Congo it's very dirty," said Mr Richard Mumbere, a Congolese cab driver. "Our government is not organised, and so it damages the environment."
Back in Rwanda, enforcing the ban, which was first adopted in 2008, involves hundreds of rules that are tricky to follow, to say the least.
Imports generally have their plastic packaging removed at customs, officials say, unless doing so would damage the goods. In that case, stores are required to remove the packaging before handing the merchandise to customers.
Food wrapped in cellophane is allowed only in hotels and only if it does not leave the premises.
Biodegradable bags are allowed only for frozen meat and fish, not for other items like fruit and vegetables because such bags still take as long as 24 months to decompose, the government says.
Potato chips and other foods packed in plastic are allowed only if the companies making them are approved by the government - after showing a detailed business plan that includes how they plan to collect and recycle their bags.
The results of Rwanda's efforts are evident in this clean country, but they may not be easy to replicate. In the United States and Europe, for example, there is a dispute between environmentalists and representatives of the plastics industry who say that bags made of alternative materials like cloth have a bigger carbon footprint than plastic ones and are not as environmentally friendly as people think. Plastic bags should be reused and recycled instead, they argue.
The authorities in Rwanda brush off criticism about the absence of similar debates in their country. The rules here are based on extensive scientific research and public surveys, they say. And their enforcement is more easily accepted in a country with authoritarian tendencies and little room for dissent.
Out of deep anxiety over national security, President Paul Kagame has hammered into shape an obedient, organised society of law-abiding and law-fearing citizens who have grown accustomed to a strong government after the 1994 genocide, in which nearly a million people were killed in 100 days.
Tough enforcement is Mr Kagame's signature style, even when it comes to developing his country. He requires all Rwandans to wear shoes, has eradicated huts with thatched roofs and has banned imports of used clothing because he says it compromises dignity.
Children here are taught in schools not to use plastic bags and to cherish the environment. Smugglers are often held in detention centres or forced to write confessions in newspapers or broadcast them on the radio. Supermarkets caught selling food in plastic packaging are shut down until they pay a fine and write an apology.
Two officials from Rwanda's Environment Management Authority recently went on a spontaneous inspection of shops in Kigali, posing as customers. By the end of the hour, they had already padlocked three stores and fined the owners a few hundred dollars each for selling bread wrapped in cellophane, using biodegradable bags for vegetables and cookies, or selling flour packaged in plastic instead of paper.
"This is very bad," said Ms Martine Uwera, one of the inspectors, towering over a store employee and jabbing her finger at a loaf of bread wrapped in plastic.
"Forgive us," the worker pleaded. "We didn't know, we didn't know." A colleague muttered: "It's not fair," under her breath.
The prohibited loaves of bread were swept off the shelves into a basket that the officials said would be distributed to hospitals, charities and orphanages. The store was closed temporarily until the fine was paid and the owner signed an apology letter.
Two stores in the vicinity suffered a similar fate, and one had it particularly bad: It was fined and lost revenue worth US$650, a sizeable amount here. Its owner Emile Ndoli, a commercial baker, tried to negotiate with the inspectors, and an argument erupted. Bread wrapped in paper, he said, went bad faster than bread wrapped in plastic. Besides, he added, customers "choose with their eyes".
"What Rwanda is doing is 100 per cent correct," he said, stealing a glance at the inspectors who stood by, listening carefully. "But I'm also a businessman, and I want a permanent solution, which won't involve losing money."