At least seven people are dead after fire tore through an apartment building in Lowell, Massachusetts.

Fire Chief Ed Pitta says crews rushed to the scene early this morning to find smoke and flames pouring from the structure.

Crews originally said as many as seven people were missing, but were able to determine that all those unaccounted for had died. The victims lived in two units at the complex.

Officials don't know yet exactly how many residents are homeless as a result, but it could be as many as 50. .

Middlesex District Attorney Marian Ryan is pledging to conduct what she expects to be a ``long and thorough review'' into the fire.

Ryan said the pre-dawn blaze in an apartment building Thursday took the lives of four adults and three children. Nine others were hospitalized with injuries not considered life-threatening.  She says it will be a ``fairly long time before we have positive identifications'' on the bodies.

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

Ryan says investigators have already contacted building ownership.

(Metro News Networks and Associated Press)