Four fires have been intentionally set in an out-of-the way area behind the former Renton City Hall on Mill Avenue in recent weeks, possibly by someone trying to keep warm.

An investigation is under way by Renton fire investigators; the reason for the fires isn’t known yet, but options include a malicious intent or they were basically camp fires.

There are no suspects.

“We are always concerned whenever we have someone lighting fires in the city,” said Fire Marshal Anjela St. John. “We hope the behavior doesn’t change into something else.”

There’s no evidence that any tenants of the city-owned building are being targeted, she said. She called the location where the fires have started an “area of convenience” with some cover.

The King County Sexual Assault Resource Center is in the seven-story building’s lowest floor.

The small fires were started on the concrete with discarded materials, she said. Accelerants weren’t used.