Three American women who were discovered dead in a Belize resort hotel room last month died from carbon monoxide poisoning, their families said.

The women’s families issued a statement saying they had been notified by officials in the Central American country Wednesday who told them the women died from “acute” carbon monoxide poisoning, likely from an instant hot water heater.

Three U.S. tourists who were found dead in a hotel room in Belize last month reportedly died from carbon monoxide poisoning.