BILLINGS, Mont. (AP) — Yellowstone County officials say it appears a mother and daughter who were found dead in their home died of carbon monoxide poisoning.

Coroner Bill Jones says they are awaiting results of blood tests, but Police Capt. John Bedford says carbon monoxide levels in the house were extremely high when the bodies were found Wednesday.

The victims were identified Thursday as 33-year-old Jessica Hicks and 14-year-old Alexis Nicholson.

Bedford says carbon monoxide appears to have come from an on-demand hot water heater that was improperly vented into the crawl space instead of outside.

The unit turned on when Hicks ran water for a shower. Officers say her body was found in the bathroom while Alexis collapsed at the top of the stairs coming up from the basement. Assistant coroner Chad Fehr says the family dog also died.