Updated

Chicago police say a man they were questioning about a fire that killed an infant, two children and a man has been released without charge.

Chicago Police Officer Jose Estrada said the man was released Thursday morning. Estrada says the criminal investigation into the Tuesday morning blaze continues and police still believe it was arson.

Police said after the fire that it appeared to have been deliberately set by someone after a domestic dispute.

Three-month-old Melanie Watson, two children ages 7 and 4, and 56-year-old Kirk Johnson died in the fire. The Cook County medical examiner has ruled the infant and Johnson's deaths homicides. Autopsies on the children are pending identification.

Federal agents are working with Chicago police and fire investigators to determine the cause of the fire.