The Harris Street house in Oxley Vale erupted in flames just after 6pm.

On Monday, Oxley Detective Acting Inspector Jason Darcy said early investigations suggested it was not deliberately lit.

"Oxley detectives and forensic police have examined the scene as part of investigations," he told the Leader.

"The cause of the fire is being treated as suspicious, but the point of ignition is still being investigated."

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The home remained a crime scene for much of the day on Monday as investigations continued.

Firefighters spent two hours battling the fire on Sunday night, after four Fire and Rescue NSW crews were called to the scene at about 6.20pm.

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None of the occupants of the home were home at the time of the blaze, and nobody was injured during the incident.

Fire and Rescue NSW Superintendent Tom Cooper told the Leader the fire had spread into the building's ceiling, with part of the roof collapsing.

"They had trouble gaining entry to the building, because they couldn't isolate the solar power," he said.

"So that was obviously a risk."

Emergency crews heard "a number of what they thought were explosions" on arrival at the scene.

Firefighters suspect gas cylinders were to blame, and after a tough fire fight, were able to extinguish the blaze shortly after 8pm.

It was then handed over to police and declared a crime scene.

"There was a fair amount of damage in the loungeroom, the fire got into the roof, they had to pull the ceiling down to get it out," Superintendent Cooper said.

"The roof collapsed a bit at the rear of the premises."

THE roof of an Oxley Vale home has collapsed after a fierce housefire took hold on Sunday night.

A Fire and Rescue NSW spokesperson said crews spent two hours battling the fire which is being treated as suspicious.

Nobody was home when the Harris Street home caught alight about 6.15pm, the spokesperson said.

Three Fire and Rescue teams as well as the hazardous materials truck were deployed to tackle the blaze, with reports of multiple explosions.

Fire and Rescue NSW Superintendent Tom Cooper said firefighters arrived to find the well alight.

The crews, two from Tamworth South and a third from the Tamworth brigade, heard loud bangs they thought were explosions inside the building, he said.

They had trouble gaining access to the structure because they couldn't isolate the home's solar panel system, Superintendent Cooper said.

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Crews then entered the home to search for occupants, but no one was home, and no one was injured in the incident.

The fire quickly spread into the roof, and firefighting teams were forced to pull down part of the ceiling to extinguish it.

The roof collapsed at the back of the property and there was substantial damage in the loungeroom, Superintendent Cooper said.

Police and paramedics were also called to the blaze, and the home was declared a crime scene about 8.15pm, when the fire was extinguished.

It was the second housefire on Sunday. A blaze sparked by unattended cooking damaged a Marius Street, North Tamworth home with smoke damage. Nobody was injured, fire crews said.

A 29-year-old driver was also injured in a third incident, a car crash on the untarred section of Whitehouse Lane on Sunday afternoon.

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