DENVER -- Investigators are trying to figure out what started a fire that destroyed a duplex in Englewood Saturday morning.

Firefighters said the fire started just after 2:30 a.m. at the home on Harvard Street.

The fire started on the west side of the building and quickly spread to the east side, said Assistant Fire Marshal Marla Wilcox of the Englewood Fire Department.

The residents of the west side of the duplex came home while firefighters were fighting the fire, Wilcox said, while the people living on the east side heard the fire start and were able to escape.

No injuries were reported.

Neighbors told firefighters one of the homeowners was using fireworks earlier in the evening, Wilcox said.

Fireworks Blamed For House Fire In Centennial

Firefighters in Centennial said a fire that caused $100,000 in damage to a home was started by fireworks.

Witnesses told firefighters that a firework landed in a tree causing it to catch on fire, said Kevin Ferry of Cunningham Fire Rescue.

The fire spread to the outside of a home Saturday afternoon and threatened the spread to the attic, Ferry said.

Firefighters were able to extinguish the fire but it caused extensive damage to the outside of the house.

All fireworks are illegal in the cities of Aurora, Centennial and Denver. Fires caused by fireworks can result in arson charges.

Ferry said investigators will interview witnesses and determine if charges will be filed.