Police in Woodstock, Ont., want to hear from anyone who took pictures or video of an apartment building during a weekend explosion and fire.

Police say photos or videos might help investigators who are sifting through the wreckage in a search for two missing residents.

Woodstock police Const. Steven McEwan says officers could be working until next week to determine whether there are bodies in the charred rubble of the three-storey building.

Police say prospects look grim for two people missing since the Sunday morning blast. Five others who were previously unaccounted for have been found alive.

Authorities have yet to determine what caused the blast, but say there's no indication of criminal activity.

Investigators are looking into a natural gas service that powered appliances in the building as a possible cause.