TORONTO (Reuters) - Thieves in the Canadian province of Quebec may have pulled off the sweetest heist of all time, siphoning off a reservoir of maple syrup from a warehouse and cleverly covering up their caper to evade detection, an industry group said on Friday.

The warehouse in rural Quebec held more than C$30 million ($30.4 million) worth of maple syrup, a whopping 10 million pounds of the amber pancake topping.

It was not clear exactly how much of the sweet stuff was taken in the heist, which occurred at some point over the last few days and was uncovered during a routine inventory check.

“We don’t know yet how much is missing - we do know it is significant,” said Anne-Marie Granger Godbout, executive director of the Federation of Quebec Maple Syrup Producers.

Numerous barrels in the warehouse were emptied of their sticky contents. The remaining barrels need to be weighed and tested to ensure the syrup inside had not been tampered with.

The robbers “were wise enough, they tried to hide their crime,” said Granger Godbout. “We just want to make sure we know how much is missing and how much is still there.”

The warehouse, some 160 kilometers (100 miles) northeast of Montreal, is one of many locations where Quebec’s maple syrup is temporarily stored ahead of sale and distribution.

The agency believes the syrup was taken to be sold on the black market. Quebec’s provincial police force is investigating the robbery.

With Quebec’s 2012 harvest expected to top 96 million pounds, the province produces some 75 percent of the global supply of maple syrup, made from the sap of maple trees.

All the syrup held by the Federation of Quebec Maple Syrup Producers is insured and the agency maintains a stockpile of syrup that it likens to a “global strategic reserve,” according to a press release.

“I can assure you there will be no shortage in maple syrup,” said Granger Godbout.

($1 = 0.9869 Canadian dollars)