A fire killed a mother and three children in a North Philadelphia rowhouse Saturday morning, officials said.

“A very difficult morning for us,” Adam Thiel, the city’s fire commissioner, said in a statement. “The worst thing for any firefighter is not being able to save a life.”

The victims were a 35-year-old woman, two boys, ages 17 and 9, and a girl, age 11, police said.

The fire was reported at 7:52 a.m. on the 3300 block of Kip Street in Kensington. When firefighters arrived, Thiel said, there was already smoke and fire on the first and second floors, and when they entered the home they found the victims. The mother was on the first floor, and the children were upstairs, police said. They were pronounced dead at the scene at 8:02 a.m..

The fire was put under control at 8:16, the Fire Department said.

An investigation into the cause was underway, Thiel said.

While the victims hadn’t been identified late Saturday, neighbors said they were a quiet family.

“She was a good person, a good mother,” said Hector Martinez, 48, a neighbor. “Nobody could say nothing about them. Those kids were always in the house.”

About 60 firefighters, medics, and support personnel responded to the blaze, he said.