BULLHEAD CITY, Ariz. (AP) — Five people, including three young children, have died in a house fire in northwestern Arizona, authorities said Sunday, adding it appeared no adults were home at the time.

Bullhead City police said the fire broke out around 5 p.m. Saturday and the victims did not make it out of the two-story duplex in that community near the Colorado River.

A city fire department spokeswoman said the five victims were ages 2, 4, 5, 11 and 13. Their names weren’t immediately released Sunday.

Authorities said the cause of the fire isn’t known yet.

Police said there reportedly were no adults home at the time, but officials gave few other details.

The fire is being investigated by the city’s police and fire departments and other agencies including the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.