DES PLAINES, Ill. (NewsNation Now) — A mother and her four daughters were killed in a Wednesday fire that swept through their home in the Chicago suburb of Des Plaines, the city’s fire chief said.

Killed in the fire in the two-story apartment building were Renata Espinosa, 6; Genesis Espinosa, 5; Allizon Espinosa, 3; Grace Espinosa, 1; and their mother, Citahaly Zamiodo, 25, according to the Cook County medical examiner’s office and fire officials. The father of the children wasn’t at home at the time of the blaze.

“I’ve been doing this for 30-some-odd years, and this is the worst day I’ve ever had,” Des Plaines Fire Chief Daniel Anderson said during a press conference.

Anderson and the state fire marshal, also at the scene of the blaze, did not give the cause of the fire, which remains under investigation.

Pabel Marrero, 52, a resident of the building, said he was in bed in the apartment just below the family’s when he smelled smoke. A person knocking on his door told him he needed to get out because the building was on fire.

“He’s screaming at me to come out ‘the house, the house is on fire’” he said.

Marrero said police arrived at the scene quickly, but struggled to get to the upstairs apartment because the door leading to it was locked.

Anderson said heavy smoke was coming from the second floor when firefighters arrived. He said they immediately went into search-and-rescue and fire suppression mode.

“Unfortunately, during our attempts we located and recovered five victims,” Anderson said.

The children were pronounced dead at Advocate Lutheran General Hospital in Park Ridge, while the woman was pronounced dead at the scene.

The house, which had been divided into four apartments, according to village records, appeared to be severely damaged.

A firefighter hurt his knee battling the blaze and a police officer was cut by debris, city officials said.

The Associated Press contributed to this report.