The intense fire broke out in a duplex in Bullhead City around 5 p.m. local time on Saturday. The five children present did not escape in time when the building went up in flames.
The five victims were 2, 4, 5, 11 and 13 years old. Their names have not yet been released. According to police, no adults were present when the fire spread.
Four of the children were siblings and the fifth child was a relative, said Emily Fromelt, spokeswoman for the Bullhead City Police Department.
The cause of the fire is still unknown. The police have opened an investigation.