POULSBO — An 80-year-old wood building on a wood dock. Probably not the best place for a cigarette break. Definitely not the place to toss your smoke when you’re done.

An inadequately snuffed cigarette was not the confirmed cause Sept. 18 of some smoldering that charred the underside of two deck boards in an alcove outside Sheila’s Portside Pub. But as firefighters removed the boards, they picked up enough cigarette butts to indicate the spot is regularly used by smokers.

In fact, all along the dock, on the side facing the Poulsbo Marine Science Center building, cigarette butts were easy to find — and within view of “No Smoking” signs placed by the Port of Poulsbo earlier in the week at the request of a city building inspector.

Poulsbo firefighters were called to the site at about 3 p.m. after smoke was reported coming from beneath the deck. Firefighters hosed the deck and a wall, removed siding, and used a thermal imaging device to measure heat coming from suspected hot spots.

Battalion Chief Shane Anderson went under the dock in a port skiff and confirmed the fire was out at 3:49 p.m. At 4:01 p.m., a firefighter with a thermal imaging device reported “no significant heat” coming from the interior or exterior wall.

A support beam beneath the exterior wall appeared to be burned. Firefighters taped off the area, to prevent people from walking over the plank-less section of deck.

The fire is being investigated by the fire marshal.