SOUTHBRIDGE, Mass. - The state fire marshal's office is investigating what caused a seven-alarm fire in Southbridge early Wednesday morning.

The town's fire chief said working fire alarms helped alert people and without them, it may have been a different outcome.

Flames broke out just before 3:30 a.m. on Union Street.

A woman who lives across the street shared this video with us and said she woke up to what sounded like explosions.

Nearly 30 people who live in the two apartment buildings are without a home, but the fire chief said everyone made it out safely.

Chief Paul Normandin said it was a fast-moving fire in the middle of the night, and it took multiple departments to help put it out.

"We called up to the total number of seven alarms for this fire, mainly for manpower and probably 30 fire departments around the Southern Worcester County area," Normandin said. "At this point in time, all the citizens involved with this fire are all at the Community Center in Southbridge, on Chestnut Street. They're receiving aid from the Red Cross and other agencies that we've already contacted."

One firefighter was brought to the hospital for a hand injury.

Two vehicles parked between the buildings were also destroyed.

State police and fire investigators are assisting the Southbridge Fire Department.