A police raid on a house in Airdrie turned up 517 marijuana plants with an estimated street value of almost $650,000, officials said on Friday.

Officers with the Alberta Law Enforcement Teams (ALERT) — including RCMP and Calgary Police Service members — executed a search warrant at the residence on Thursday.

The furnace and hot water tank had been rigged to feed carbon dioxide to the plants in the growing operation, investigators said in a release.

Officials with Alberta Health Services inspected the home and determined that it is no longer fit for human habitation.

No charges have been laid yet. The investigation is continuing, police said.