B.C. Mounties have busted a Maple Ridge medical marijuana operation that they say was exceeding its allowed production limit by almost seven times to feed street-level drug trade.

Police raided a property in the 16000-block of 112th Avenue on May 26 and discovered 1,490 pot plants growing inside a barn. The site was licensed by Health Canada to grow medical marijuana, but only 220 plants.

Three men in their mid-30s were arrested on scene, but only one of the men was named in the marijuana licence. The other two men have histories of illegal drug trafficking and all three were known to police, according to RCMP Const. Michael McLaughlin.

"A lot of people don't realize there is a potential for abuse with medical marijuana licences that is absolutely being exploited by criminals," McLaughlin told ctvbc.ca.

"This is part of a growing concern."

RCMP also seized an R44 helicopter, two pickup trucks and three trailers they believe were set up to be used as mobile grow-ops.

McLaughlin said that drug-sniffing dogs detected the scent of marijuana in the helicopter, suggesting that it may have been used to deliver drugs throughout Metro Vancouver and maybe even to the U.S.

"We know that a lot of the marijuana produced and trafficked in B.C. heads to points south of the border," he said.

"That is a possibility that we're going to explore."

The three men are expected to face charges of drug production, and police say more arrests are expected.

McLaughlin said it is now up to Health Canada to decide if the medical marijuana licence will be revoked.