PITTSFIELD — Careless disposal of smoking materials is suspected in a structure fire early Monday morning that extensively damaged a second floor porch on a Merriam Street dwelling.

Deputy Fire Chief Matthew Noyes reported that four fire vehicles responded to the blaze, which was showing from a front porch at 75 Merriam St. when fire crews arrived. The fire was quickly knocked down, he said, and there were no reported injuries.

A search of the building was conducted to ensure to check for any extension of the fire. Damage was reported to be extensive on the porch with minor interior damage on the second floor and minor water smoke and water damage.

The incident was under investigation Monday by the PFD Fire Investigation Unit.