CHICAGO — A fire at a Chicago apartment building that appears to have been deliberately set killed four people Tuesday, including three children, police said.

It took around 200 firefighters three hours to put out the blaze, which began about 1:30 a.m. in a three-story building in the South Chicago neighborhood. Witnesses said they saw residents leap from windows to escape.

A preliminary investigation indicated a person returned to the building after a domestic dispute and set fire to the rear porch, police spokesman Anthony Guglielmi said. Officers were searching for a ‘‘person of interest wanted for questioning,’’ he said.

An infant was pronounced dead at a hospital, and two other girls — ages 4 and 6 — and a man were found dead later on the third floor, said Deputy Fire Commissioner Arriel Gray.

The Cook County medical examiner’s office identified the baby as 3-month-old Melanie Watson. Three other people were hospitalized, according to the Chicago Fire Department’s media office.

Arson investigators were on the scene. ‘‘The fire was suspicious in nature. It’s under investigation,’’ Gray told reporters. He said the exterior and interior stairwells were burned out, preventing firefighters from attacking the fire from inside the building.

Witnesses told reporters they saw several people jumping from windows to escape.

Gray said it was unclear whether the baby was dropped from a window or brought down a ladder.

Associated Press