Around 8pm firefighters were "dampening down" and ventilating the restaurant, she said, and a fire investigator was heading to the scene.
A house in Weymouth was "well ablaze" when crews arrived, Ruru said.
Four engines were initially called to the scene around 7.15pm, but two were stood down when first responders managed to get the fire under control.
Ruru said the fire was thought to be suspicious and an investigator had been sent to the Tonuitangi St address.
Police and ambulance also attended the Weymouth fire and one person was treated by paramedics for smoke inhalation.
A car had also caught fire on the Southern Motorway, between Mt Wellington and Princes St, southbound, Ruru said.
No one was in the car when fire crews arrived so it was believed no one was hurt.