Last Updated Jul 10, 2014 10:06 AM EDT
LOWELL, Mass. -- Authorities said seven people were dead after an early morning fire in a apartment building in Lowell.
Nine people were taken to the hospital with non-life-threatening injuries.
The three-alarm blaze was reported at about 3:30 a.m. The building was already engulfed in heavy flames when firefighters arrived.
Witnesses told CBS Station WBZ that people were tossing babies out of second-floor windows in an effort to get them to safety.
One fire captain sustained a leg injury. At one point part of the roof collapsed, forcing firefighters to evacuated.
Deputy Fire Chief Patrick McCabe said 48 people lived in the building, which had businesses on the ground floor and apartments on the upper floors.
At a morning press conference, State Fire Marshal Stephen Coan confirmed that the fatalities (four adults and three children) were found in two apartment units on the building's top floor.
"It's a tragic day in the city of Lowell with a horrific fire," said Lowell Mayor Rodney Elliott. "The entire city mourns the losses for families that have lost victims in this fire."
He said donations to the Red Cross were being accepted, and announced a relief fund has been set up for the victims' families.
"They have nothing. They've lost everything in this fire," said Elliott.
Lowell resident Rothe Proeung received a call at 4 a.m. about the fire. He told WBZ his two children were sleeping at their mother's apartment in the building. "At the time I was thinking about my kids. Where are my kids? Are they dead? Are they alive?"
Proeung said he found his two children outside the building. Both had suffered injuries but are expected to be OK. They were among those taken to area hospitals.
Coan said the fire's cause remains under investigation. Officials noted that witnesses reported a sound like fireworks, but said no conclusions could be drawn.
Fire officials said that there was an alarm system in the building, but no sprinklers.