Island County Sheriff Mark Brown said “a series of extremely suspicious fires” on South Whidbey points to the possibility of a serial arsonist at work.

The seventh suspicious fire occurred Friday night at an old storage shed on Swede Hill Road, which is a Clinton address. But Brown said all of the other six “suspicious and possibly related” blazes occurred in and around Freeland.

“They all had the same MO and occurred at night,” the sheriff said. “I’m really concerned about it.”

Investigators believe a fire that destroyed a landmark squash barn on Central Whidbey May 17 probably wasn’t related to the arson spree because it was outside of South Whidbey, but Brown said the barn fire was definitely suspicious.

Brown has beefed up nighttime patrols on South Whidbey, but he’s hoping for help from residents. He’s asking folks to be vigilant of outbuildings and to be careful where they store flammable materials.

“People should be sure to report any suspicious activity,” he said.

Over the last month, the seriousness of the arson targets has quickly progressed. The latest targets were a home under reconstruction and a shed.

“Starting with trash bins and going to buildings is frightening,” Brown said.

The first fire occurred May 2 at the Trinity Lutheran Church in Freeland. It started in a recycling bin.

The second fire started May 6 in a pile of plastic at the Island Recycling Center.

The third fire began May 11 in a portable toilet on the side of North Bluff Road and Willow Pond Lane, where county crews were doing some work.

The fourth one was a brush fire May 15 on Shoreview Drive in Freeland.

The fifth fire was May 28 at Double Bluff Beach. The arsonist torched the county-owned restrooms, burning them to the ground. The loss is estimated at $80,000.

The sixth fire was May 30 on Cameron Road. An unoccupied home that was being remodeled into office space was set ablaze.

The seventh and latest fire was the old storage shed on Swede Hill Road.

Anyone with any information about the fires should call 911 or the Sheriff’s tip line at 679-7319, or on South Whidbey, call 360-321-5113, ext. 7319.