COULEE CITY, Wash.—Grant County Sheriff’s Office investigators are looking into the deaths of two people who were found dead in their home Monday night.

GCSO officials said they believed the two had died of carbon monoxide poisoning at their home on the 500 block of West Walnut Street in Coulee City.

Grant County officials said deaths in Grant County due to carbon monoxide poisoning have happened in the past, including an incident on November 26, 2007 in Royal City.

In that incident three children died and two more were hospitalized after being overcome by carbon monoxide from a generator which was running inside their home. The generator was powering electric heaters during a power outage, according to GCSO authorities.