An early-morning fire Tuesday engulfed a house in northern Kentucky, killing five, including three children.

The names of the victims were not immediately released but the three children are believed to be siblings who died with their mother in the fire that was first reported at 1 a.m. local time. Another adult male was found in a separate apartment.

The fire is under investigation, which is standard protocol for such cases.

Maysville Mayor David Cartmell says the apartments were in five brick row houses with three stories each in an older section of town.

Ron Rice, the Maysville fire chief, told FoxNews.com that the mother and three children were located in the same area of the apartment, which may indicate that they were trying to escape or huddling to make an exit plan.

"It's just a tragedy," he said.

Fox News' Edmund DeMarche and the Associated Press contributed to this report