The rising demand for electronic cigarettes has led to more seizures of these items, which cannot be sold or imported here.
Last year, the Health Sciences Authority (HSA) confiscated 5,356 e-cigarettes, almost three times the number seized the year before. In 2009, just 10 units were confiscated.
The sharp spike in recent years comes as the alternative smoking product gains popularity here.
Also known as vapers, battery-powered e-cigarettes try to simulate smoking by heating and atomising liquid nicotine stored in a small, replaceable cartridge.
HSA said its Tobacco Regulation Branch carries out regular online surveillance to deter the sale of e-cigarettes locally. But it also noted that the number of such cases remains small.
Instead, the steep rise in the number of e-cigarettes being seized could be due to the "increased number of vaporiser companies sprouting overseas, as well as increased promotion and awareness of vaporisers through overseas media channels".
Checks by The Straits Times show that e-cigarettes are gaining popularity here, evident from the many online forum discussions on where to buy e-cigarettes.
Since the sale of e-cigarettes is illegal here, local users turn to overseas websites or purchase them when abroad.
E-cigarette users The Straits Times spoke to said they believed the product is banned here "just like chewing gum". However, they were unsure if it is an offence to own one.
Under the Tobacco Act, the import, distribution, sale or offer for sale of anything that resembles a tobacco product is prohibited. Since 2011, HSA has prosecuted eight people for selling e-cigarettes. This year, three of them were fined close to $100,000 for peddling the product online.
Buying e-cigarettes from overseas websites or bringing them into the country in hand luggage is also considered importing, which is illegal. Offenders may be fined up to $5,000 for the first time, and up to $10,000 subsequently.
But it is not illegal to own an e-cigarette purchased locally. The Straits Times understands that the law is currently being reviewed.
Ms Felicia Tan, 35, a marketing manager who bought hers during a holiday in Switzerland, said: "I bought it out of curiosity as the tip of the e-cigarette lit up like a real cigarette when I inhaled. But it didn't give me the same experience as smoking a real cigarette. I have since thrown it away."
Another user, who declined to be named, said he uses an e-cigarette as a substitute for cigarettes, and he has since managed to quit smoking.
The 36-year-old sales director had paid US$100 (S$126) for an e-cigarette from the United States, and gets his refills from Johor Baru for RM6 (S$2.30). Each bottle of refill can last for about three months, he said.
However, HSA said there is no conclusive scientific proof to back claims that e-cigarettes are effective in helping smokers quit.
A spokesman said: "We are monitoring the situation, but it will be premature to speculate whether there are any trends at the moment.
"We will continue to conduct surveillance to deter e-cigarette sales and also work closely with the Immigration and Checkpoints Authority to prevent such products from being brought into the country."