A resident of the house at 149 New Amwell Road reported the fire at about 2 p.m. and was able to escape with a family dog.

Somerset County Prosecutor Wayne J. Forrest said the fire appeared to have started in the back of the house, possibly under a deck.

"Apparently, it was quite an extensive fire," Forrest said.

The Somerset County Prosecutor's Office Arson Task Force investigated the scene, as is standard procedure, Forrest said.

Witnesses say the flames towered high over the house.

"I saw the smoke down on South Branch Road," said Joanne Brandt, whose sister, Debby Micol, lives next door to the destroyed home.

After the fire, Brandt and her husband, Greg, a firefighter with Hillsborough Fire Company 1, sat under Micol's deck watching the other firefighters finish their work.

Micol said she was at work when her daughter called to tell her the neighbor's house was on fire, so she rushed home.

Jen Donnelly, a resident of the Beekman Gardens apartments behind New Amwell Road, watched with her son Jack, 5, as firefighters hosed down the house after dousing the blaze.

"If you look at the tree in front of the house, it's all black," she said. "It had to be a nice fire if all the trees are black."

Mike Navarro, a resident of Fisher Drive, said he was driving on Raider Boulevard when he saw the smoke and came by to check out the scene.

Further details about the fire, including the cause, were not available at press time.