TULSA, Oklahoma - The fire marshal is investigating a fire at a car wash in Tulsa early Thursday morning.

The fire damaged the old Splash Car Wash building on 71st Street.

After putting out the flames, firefighters say they found someone's belongings scattered all over the place, but no one was inside.

The building has been boarded up for a while and firefighters say homeless people have been staying here recently.

The Tulsa Fire department says it appears it was started by someone trying to keep warm but investigators are still working to determine if that was definitely the cause.

Most of the damage was contained to the inside of the building.