Police are questioning a possible suspect in an apartment building fire that killed three children and a man.

Police spokesman Frank Giancamilli said Wednesday that investigators have been questioning the person since Tuesday. No charges have been announced.

Police say a preliminary investigation indicates someone deliberately set fire to the building early Tuesday after a dispute. Around 200 firefighters worked for hours to put out the blaze at a three-story building in the South Chicago neighborhood.

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

The Cook County Medical Examiner's Office identified the baby as 3-month-old Melanie Watson.