Authorities say four adults and three children have died in a fast-moving Massachusetts apartment fire, and nine others have been hospitalized with non-life-threatening injuries.

Middlesex District Attorney Marian Ryan is pledging to conduct a "long and thorough review" into Thursday morning's fire in Lowell that had tenants jump or hand children to safety.

She says it will be a "fairly long time" before the victims are identified.

Police and firefighters rescued people who were jumping and dropping from the windows, Ryan said. The fire broke out on the third floor of a building, the age of which was unknown, Ryan said.

Lowell Fire Chief Edward Pitta said firefighters were forced to evacuate when the building's roof started to collapse. One fire captain suffered a leg injury but is expected to be OK.

The investigation will include whether the alarm system was working and whether there were fireworks in the building, as some witnesses described hearing explosions.

The early morning fire took place in the heart of the Cambodian community in Lowell, and the victims are believed to be Cambodian. Lowell area has the highest concentration of that immigrant population in the eastern part of the U.S.

“We’re going to be providing free translation services for whoever needs it because we have a staff of translators here who will donate their services for free," said Voop De Vulpilliers, director of Cambodian Mutual Assistance Association. "Finally we are going to be working hard to rally the community to donate to the fund that’s been created by the mayor.”

Neighbors and friends of the victims are still gathering behind the yellow police tape to watch fire fighters put out the smoking embers. They’re expressing sadness and anger, at the building’s condition before the fire and questioning whether it had functioning smoke detectors.

Ryan says investigators have already contacted building ownership.

Mass. State Fire Marshal Stephen Coan said the last time there was a fire of this magnitude was 20 years ago.

"There was a Christmas Eve fire in 1994 in a single-family home in North Attleboro that unfortunately took the lives of a whole family," Coan said. "That is the last time we reached this number. A fire of the magnitude of this loss, we go back in history."