Whidbey firefighters were busy Wednesday responding to six brush fires — including three suspicious blazes — on the North End and in Central Whidbey.

North Whidbey Fire and Rescue responded to five fires Wednesday afternoon from 3-5 p.m., according to Battalion Chief Steve Lacy.

One fire grew to 7 acres in the woods on the Navy’s Seaplane Base; the Navy’s firefighting crew also fought the flames.

Firefighters were called out yet again for a fire in a grassy area off Hoffman Road.

North Whidbey firefighters, Oak Harbor firefighters and a brush truck from Mount Erie Fire Department from Fidalgo Island responded, Lacy said. It grew to 3 acres before crews controlled the flames and then the state Department of Natural Resources took over the effort.

North Whidbey crews also helped Oak Harbor firefighters put out a fire near Goldie Road, and later there were two fires on Boon Road.

North Whidbey Fire and Rescue Chief John Clark said that the fire on Hoffman Road and the two fires on Boon Road are considered suspicious because they had “no obvious sources of ignition and no smokes materials” in the surrounding area. There were also no witnesses. It is undetermined if they are cases of arson, he said, and will likely stay listed as undetermined because the agency has no definitive information about how they began.

Central Whidbey Island Fire and Rescue crews also responded to a fire that day.

Deputy Chief Jerry Helm said a fallen power line on Wanamaker Road sparked a 30-by-40-foot blaze.

Last Friday, Langley Mayor Scott Chaplin sent an email to residents alerting them to four fires that happened over a three-day period and urged them to prepare for “smoke season.”

Island County was included in an air quality alert announced by the National Weather Service Thursday as smoke from British Columbia is blanketing the region.

Smoke agencies are predicting that the air quality in the Puget Sound region will be unhealthy for sensitive groups through Saturday, when the wind direction is predicted to shift.

Clark asked people to adhere to current burn ban requirements that put the kibosh on all outdoor burning, including campfires, for the foreseeable future.

He also asked people to be careful when throwing away their cigarettes and to stop using fireworks, the latter of which is prohibited by the burn ban.