The fire was reported at about 5 a.m. and was ``pretty much under control'' by 7:20 a.m., said Stephen Benner, deputy chief of the fire department.
A 21-year-old mother and her two sons, ages 1 and 2, died in the fire, which started on the first floor of their house, officials said.
The woman was found still in bed. One of the children was found in a second-floor bathroom and the other near the bottom of a flight of stairs, officials said. Their names were not immediately available.
Several other family members escaped the fire, authorities said.
``It's going to be hard. It's a tragedy,'' said Samuel Portis, the uncle of the woman who was killed.
One firefighter was taken to a hospital with a shoulder injury.
Four of the five homes had been occupied and the American Red Cross responded to provide displaced families with shelter, food, clothing and counseling, the organization said.
Fire officials and the Mercer County Prosecutor's Office were investigating the cause of the fire.
