Four adults and three adults perished in an apartment-building fire early Thursday morning.

According to the Boston Globe, the three-alarm fire happened around 4 a.m. in the city of Lowell, about 25 miles outside of Boston.

In addition to the deceased, nine people were hospitalized with serious injuries, one firefighter suffered a leg injury and some 50 people were left homeless after the blaze.

“Today is a tragic day in the city of Lowell with this horrific fire," said Mayor Rodney M. Elliott. “The entire city mourns the loss."

The victims who died in the fire have been identified as Torn Sak, his girlfriend, Ellen Vuong and three of their children, a 7-year-old girl, a 9-year-old boy and a 12-year-old boy. The couple also had two other sons, but they were able to make it out of the building. A family member of 38-year-old Tina Christakos’ identified her as another one of the victims. The seventh person, believed to be a male in his 70s, has not yet been named by authorities.

The Associated Press reported the one of the victim’s siblings, Thearan Sak, said that his brother liked fireworks and had some stored away in his unit. However, officials are still investigating that information and what the actual cause of the blaze was.

The tragedy marks the second deadliest fire in Massachusetts in two decades.