A man is facing 337 charges after police seized 33 guns from a Pickering home.
Durham Regional Police say firefighters responding to a carbon monoxide alarm at the home on Wednesday noticed a suspicious substance in the basement.
Officers, aided by the provincial police clandestine lab team, located an unidentified substance along with 33 guns and other prohibited devices, such as overcapacity magazines.
Investigators say the substance has been sent for testing.
A 33-year-old Oshawa man faces charges that include careless storage of a firearm, unauthorized possession of a firearm and possession of a restricted or prohibited firearm.
Anyone with information related to the investigation is asked to call police.