London police say evidence of marijuana oil extraction has been found at the scene of an explosion and fire on Friday in the city's south end.

Emergency crews were called to 1217 Southdale Road East around 8:15 p.m. following an explosion and fire that left three families homeless.

The Arson Unit of the Criminal Investigation Division is continuing with the investigation and has found evidence of marijuana oil extraction being conducted within the unit.

Police say there is no further danger of any chemicals regarding safety to the public.

A man who was seen running from the unit shortly after the explosion has not yet been identified and anyone with information is asked to contact police.

The investigation is ongoing.