PORTLAND, Maine (AP) - Sticky-fingered thieves are stealing the sap right out of Maine's maple trees.

With little more than a spout-like tap and a bucket, people are looting the liquid out of trees on private property and hauling it away to turn into sweet maple syrup.

There's been an increase in reported sap thefts the past couple of years, but Maine Forest Service rangers aren't sure why.

"It could be that landowners are more willing to contact us. But it also may be that more people are venturing out into the woods to try their hand at this," Ranger Thomas Liba said.

Syrup is big business in Maine between late February and mid-April, when conditions are just right for sugar makers to extract sap from maples and boil it down to syrup over wood fires. The state last year produced 1.3 million litres, tying it with New York as the No. 2 syrup-producing state. Vermont, the top state, produced 2.8 million litres).

At US$50 (S$62) a gallon (3.8 litres) or more on the retail level, Maine-made syrup is pricey, selling for 13 times the price of gasoline. The price varies slightly from year to year, but it has not been showing an upward trend in recent years.

Syrup-related thefts are nothing new. Just this week, a Vermont syrup-maker reported the theft of equipment from his sugarhouse.

And Maine's sap thefts are small potatoes compared with syrup heists that have been reported elsewhere. Thieves last fall stole nearly US$20 million worth of syrup from a Quebec warehouse that stocked thousands of barrels of the amber liquid.

Still, the thefts raise the hackles of rangers and landowners alike: The sweet-toothed swindlers aren't just trespassing, they're damaging valuable trees.

With gouges and large holes, the trees are more susceptible to decay and disease. And they also carry less value in the marketplace.

The best maple trees are highly sought-after for veneer used in making cabinets and furniture or as logs that are suitable for processing at a sawmill. But when the trees are damaged they're only suitable for less-profitable uses, such as pulpwood for pulp plants or for biomass plants.

The tapping operations typically involve 20 to 100 taps, usually by people who simply pull up alongside a logging road and drill holes into the closest trees, she said. They then catch the sap in buckets, milk jugs and other containers.

Mr Liba said he's not aware of anybody being criminally charged for illegal tapping, but he caught one person in the act this year.

That man is now working with the landowner and a mediator on how to make amends.

People sometimes think because Maine has a long tradition of open access to land for hunting and fishing, the right extends to other things as well - including tapping trees, Mr Liba said.

"I think they're viewing it as an extension of being able to go out and use property without permission," he said.