More than 150 suburban Boston firefighters battled a massive eight-alarm fire Sunday that engulfed an apartment complex under construction.

No injuries were reported at the site of the blaze in Waltham. The fire broke out just before 4 a.m. and was still burning at 10 a.m., six hours later. Gusty winds hampered efforts to bring the blaze under control.

Waltham Fire Chief Paul Ciccone said just before 7 a.m. that the complex’s five buildings had collapsed and were a “large pile of debris,” The Boston Globe reported.

Ciccone said no sprinklers were in place, which also allowed the fire to spread, Fox 25 Boston reported.

He said firefighters heard explosions as they fought the fire.

"Multiple explosions during the fire...something to do with the construction material -- could be propane, anything like that," Ciccone said, according to the station.

He said it was too early to say what caused the fire.

Nearby residents from two apartment buildings for the elderly were evacuated due to the smoke, the station reported.

Fox 25 reported that new development involved the construction of 400 apartments.

NECN-TV interviewed a person who was evacuated.

“There was ash raining down on our house and they were spraying down our house with water to make sure it didn't catch on fire,” the person told the station. “Then they said, 'you want to leave, leave now.'"