LOWELL, Mass. (WHDH) -
Investigators are back on scene Friday of deadly building fire that took the lives of seven people, including three children, in Lowell.
Officials are expected to use a big crane to start digging through debris and peel back layers so investigators can get in and pinpoint exactly where the fire started.
Lowell Mayor Rodney Elliott said he spent 13 hours straight at the scene talking with survivors and said it's unclear whether smoke detectors went off.
"Moments before, I did ask, did you hear smoke alarms, very faint as it may be," Elliott said.
The state fire department is promising an extensive investigation to look at every aspect of the building and the fire. Middlesex District Attorney Marian Ryan is pledging to conduct what she expects to be a "long and thorough review" into the fire.
The investigation will include whether the alarm system was working and whether there were fireworks in the building, as some witnesses described hearing explosions.
A Facebook photo from one of the victims shows a stash of fireworks and investigators are trying to determine if they possibly played a role.
"He was a good father, every time there was a season like that he would let his kids out and let them take the kids have a good time," said Thearan Sak, whose brother was killed in the fire. "It just happened the house caught on fire and i'm sure that made the fire even worse."
Sak's brother lived with his girlfriend and five kids, only two of the kids made it out alive.
One of the other victims was Tina Christakos.
“Her and her girlfriend was coming out with her boyfriend and somehow her boyfriend lost her hand or whatever and he got out and they died,” Tina’s uncle, Bobby Christakos, said.
The fire on Branch Street started at around 4 a.m. Thursday and resulted in the deaths of seven people that became trapped in two third floor apartments, including five from a family of seven.
Around 50 people were displaced. 10 were transported to the hospital with serious but non-life threatening injuries.