No one was injured in the afternoon blaze at Namaste India, they said.
"They were doing a patch job on the roof and the tar ignited," one said. "They tried to douse with a garden hose."
Flames spread down into the walls on the northeast corner of the building.
The building wasn't evacuated until firefighters arrived in response to an alarm triggered by the blaze, responders said.
Township firefighters and Mahwah Rescue 1 members were assisted by their colleagues from Suffern and Tallman in saving the building after thermal cameras showed flames behind the walls.
All utilities were shut off, which will keep the restaurant closed until repairs are made and the township Board of Health gives the owners the OK to reopen.
Namaste India opened last year on what formerly was the longtime site of the Kingsbridge Diner.
Franklin Turnpike was temporarily closed at Cedar Hill Avenue and Fox Lane.
VIDEO: Rockland Report
Click here to follow Daily Voice Cresskill-Closter and receive free news updates.