NAGASAKI (Kyodo) A mother and her two sons died in a residential fire in Nagayo, Nagasaki Prefecture, police said Sunday.

The fire started at the home of Mutsuyo Kai, 73, at around 9:35 p.m. Saturday, killing her and her sons, Hideaki, 50, and Horoaki, 47, according to the police.

All are believed to have died from carbon monoxide poisoning, the police said, who started an investigation into the cause of the blaze.