​4 children killed in fire on Chicago's South Side

Four children were killed and two adults were critically injured in an apartment fire early Monday on Chicago's South Side, reports CBS Station WBBM.

The first 911 call came in around 3:30 a.m. from the 11200 block of South Vernon Avenue in the Roseland neighborhood. When firefighters arrived at the scene, they found heavy fire coming from the second and third floors of a courtyard style building, and two adults on the ground outside.

WBBM correspondent Mike Puccinelli reports that, according to witnesses, two adults were screaming for help from a third floor apartment, because they were unable to reach the children trapped in the back of the apartment, before they jumped.

They were taken to Advocate Christ Medical Center in Oak Lawn in critical condition.

Four children were found dead inside the apartment. All are believed to be under the age of 13.

The blaze appeared to start on the second floor of the 18-unit apartment building at about 3:30 a.m., authorities said.

Chicago Fire Department Chief Michael Fox told reporters at the scene that the first firefighters to arrive found "heavy fire blowing" from the building's windows.

"We had to force the doors to search for other victims," Fox said. "We're still putting the pieces together."

About 50 other residents escaped the fire, authorities said.

The fire gutted multiple apartments in the building.

Some residents told WBBM that smoke detectors had been installed in the building, but they believe only one was working. Others said they did not hear any smoke detectors at all, and were awakened by the victims' screams for help.

"I saw two people. They dived out the third floor window. They were screaming, 'Help! Help! Help! Our apartment's on fire!'" Demonte Gray said.

The cause of the fire was under investigation.