PULLMAN, Wash. – Fire damage to the walls of a Pullman apartment were caused by month-old smoldering briquettes, fire investigators determined Sunday.

Firefighters were called to the apartment units at Northwest Terre View Drive and North Grand Avenue around 10:30 a.m. for a report of a fire under the deck of unit 34. Arriving responders found a resident had tried to use a fire extinguisher to put out the fire, but smoke was still coming from under the wooden deck and the walls around a stairway.

Firefighters extinguished the fire by cutting through the siding.

Deputy Fire Marshal Tony Nuttman said the resident told him the last time he used his barbecue was nearly a month ago. He said he set the pan with the briquettes on the wooden deck next to the vinyl siding.

Nuttman said there was no other ignition sources for the fire other than the briquettes, even though they sat on the deck reportedly for about a month.

Nuttman added that fire officials have before said a variety of agents can lie dormant for weeks and later ignite. The briquettes were pebble-sized, but with recent weather conditions, were able to ignite the vinyl siding and wood deck.

Fire officials recommend putting used briquettes in a bucket of water to ensure they are put out.

Nuttman estimated the damage to the apartment complex to be around $3,000 and no one was injured in the incident.