Improperly discarded smoking materials caused last week’s mobile home fire in which a dog was killed, Lawrence fire officials said.

Following the fire department’s investigation, the Dec. 12 fire at a mobile home at 1908 E. 19th St. has been ruled accidental, caused by improperly discarded smoking materials, Fire Chief Mark Bradford said this week.

Bradford said damages to the structure and its contents were estimated to be at least $20,000.

All occupants had evacuated the home unharmed when firefighters arrived about 11:50 a.m., the fire department said previously.

Fire crews rescued two dogs from the home and turned them over to the Lawrence Humane Society, but one of the dogs died from injuries received in the fire.

The Douglas County chapter of the American Red Cross was helping the displaced family, and the humane society was helping them with the dog that survived, according to the fire department.