The Quebec Federation of Maple Syrup Producers says the theft of a "large quantity" from the warehouse in St-Louis-de-Blandford was discovered during a routine inventory check.
The burglarized warehouse held more than 4.5 million kilograms of maple syrup valued at over $30 million. The exact amount of the theft was not disclosed.
Empty barrels found on the site suggest their contents had been emptied into other containers for illegal distribution.
The syrup is insured but the federation said it is crucial to find the robbers because its illegal sale will affect the entire industry.
Quebec, which had a normal harvest, helps supply markets that have had periods of weaker yield and are considered by some as a global strategic reserve.
Several regions of the United States had a very low harvest in the 2012 season, the federation said.
Federation president Serge Beaulieu said Friday the warehouse was well-protected.
"The federation always acts with caution to protect producers' harvests," he said. "The St-Louis-de-Blandford warehouse had been secured by a fence and locks and visited regularly."
The syrup was in temporary storage at the warehouse and was slated to be moved to a new facility in the coming weeks.
Quebec provides between 70 and 80 per cent of the world's maple syrup and two-thirds of the Canadian production exported to the United States, according to the federation.