BUTLER, Pa. (KDKA) — Three people were found dead in a home in Butler County from possible carbon monoxide poisoning, sources said. First responders were called to a home on College Street in Butler at around 5 p.m. on Tuesday.

Authorities believe carbon monoxide poisoning caused the deaths of three people found in a western Pennsylvania home this week, but investigators have yet to determine what led to the deadly exposure. According to the Cleveland Clinic, carbon monoxide poisoning kills over 400 people per year in the United States.

"If you have a gas furnace, if you have a gas water heater, you know, you're heating your house with your fireplace, that's typically where you'll see that," said Jones. "So you can see carbon monoxide if you have a gas heater throughout the year."

Three people found dead in a western Pennsylvania home this week apparently died from carbon monoxide poisoning

There’s a large emergency response at a Butler home after three people were found dead. Channel 11 saw firefighters, police and medics at a home on College Street on Tuesday afternoon. We’ve learned that three people were found dead from possible carbon monoxide poisoning.