The Fleet Reserve Building in Oak Harbor was damaged in a mid-morning fire Sunday, the Oak Harbor Fire Department reported.
Fire Chief Ray Merrill said the fire started inside the structure but the cause has not yet been determined.
An investigation is ongoing.
A witness reported seeing smoke coming from the roof of the building, which is in the southeast area of the city, at 10:38 a.m. Oak Harbor firefighters responded and arrived within four minutes, according to a press release from Merrill.
Fire crews entered the structure to find heavy smoke on the first floor with fire above a walk-in cooler in the kitchen area. The flames extended to the second floor and the attic.
The press release states that the command officer on scene requested mutual aid from Navy Region Northwest and North Whidbey Fire and Rescue.