A fire Monday evening at a Lawrence duplex was caused by “misuse of an open flame device,” according to a news release Tuesday from Lawrence-Douglas County Fire Medical.

Precisely what kind of device was not clear Tuesday.

Firefighters responded shortly before 7:30 p.m. Monday to the fire at 1518 W. 26th St. All of the duplex occupants had safely left the building before the firefighters arrived.

Heavy smoke and flames were coming from the rear of the one-story wood-framed duplex. The incident was upgraded to a second alarm after firefighters arrived. The fire was brought under control around 8 p.m.

The Douglas County Chapter of the American Red Cross is currently assisting the displaced occupants.

Damages are estimated to be approximately $125,000, according to Division Fire Chief Eve Tolefree.