An Oshawa man is facing 337 charges after 33 guns and other “prohibited devices” were seized from a Pickering residence on Wednesday, police say.

The weapons were discovered after emergency crews responded to a carbon monoxide alarm at a home on Liatris Drive, in the area of Brock Road and William Jackson Drive.

Upon arrival at the scene, Pickering Fire notified Durham Regional Police after they located a “suspicious substance” in the basement of the home.

The Drug Enforcement Unit then obtained a search warrant for the residence. Along with the OPP Clandestine Lab team, Durham police located and removed the unknown substance from the home.

The substance has been sent for testing, police said.

Police also allegedly located 33 guns and other prohibited items, including at least two overcapacity magazines, inside the home.

The firearms included a large number of Glock handguns, one rifle and a Tec-9 submachine gun.

Maisum Ansari, 33, is now facing 337 firearm charges, including multiple counts each of careless storage of a firearm, unauthorized possession of a firearm, possession of a restricted or prohibited firearm knowing its possession is unauthorized and possession of a prohibited device.