Hudson, NH – An explosion and fire that severely damaged a duplex appears to be accidental, but investigators haven’t yet reached a definitive cause.

Nine people were left homeless Monday after the 10 Dugout Road structure caught fire, not long after an energy company had examined the building’s propane supply.

The state fire marshal’s office is investigating with the assistance of the Hudson Fire Department. The cause remains unknown, but it is believed to be accidental, Hudson Fire Prevention Officer Steve Dube said Tuesday.

Eastern Propane & Oil employees examined a propane leak and told residents it was safe to return to their homes before the blast, according to a resident. The company is helping fire investigators, Vice President Jeff Taylor said Tuesday.

Iris Gaudet, who lives in apartment 10A, said a Comcast technician told her he couldn’t work in her unit because propane was leaking from the side of the building rented by the family in 10B. Gaudet also said she smelled natural gas during the day.

Deputy Fire Chief Neil Carter said the department responded to the area earlier Monday for the odor of natural gas and turned off the gas to the building before calling Eastern Propane & Oil. Firefighters determined there were no hazards so they left the scene, he said.

Workers from the company arrived and eventually told the families that the building was safe and turned the furnaces back on, Gaudet said.

Later, the living-room windows of 10B blew out and fire started coming up from the cellar, Hudson Fire Chief Shawn Murray said.

Taylor said he has a better understanding of what Eastern Propane & Oil employees did on the call but couldn’t comment because of the investigation.

The company follows “stringent” state and federal guidelines when checking for odors and leaks, Taylor said. When asked if the employees who went to 10 Dugout Road followed those guidelines, Taylor said that is being reviewed.

The fire caused more damage to 10B and caused smoke and heat damage to 10A, Dube said.

All nine people in the building escaped without injury, even though when first responders arrived, the fire had spread to all floors, Murray said.

In light of the explosion, Hudson Fire officials reminded residents to take precaution when smelling gas: extinguish smoking materials, evacuate the building or vehicle immediately, don’t light a match or use a phone, shut off gas supply valves outside the building and stay out of the structure until fire officials have inspected and cleared the building.