"It's a big loss", a fire manager says of the damage a blaze caused to popular Dunedin restaurant No 7 Balmac.

Emergency services were called to the Maori Hill restaurant in Balmacewen Rd about 12.50pm today where crews battled a "well-involved fire" in its ventilation system.

The fire was mainly in the roof, large parts of which needed to be removed to allow firefighters access.

The building was evacuated during the busy lunch service and no one was injured in the fire.

There were seven fire appliances at the scene at the peak of the blaze.

Fire and Emergency New Zealand East Otago assistant area commander Craig Geddes said there was “significant” damage throughout the two-storey building.

"It's right through the entire restaurant. Not just from fire, but water damage."

However, the fire had been contained by 2.30pm.

Crews were salvaging what they could after water used leaked into the bottom floor of the restaurant.

The cause of the blaze was unknown, but a fire investigator had been called.

Damage was worst in the ventilation system in the building’s roof, Mr Geddes said.

"It's a big loss."

No 7 Balmac business owner Katrina Toovey was at the scene this afternoon, but unsure of the extent of the damage.

"There are a few hoses going in there, so there's a reasonable amount of water which will have fallen on something."

It was not known how long the restaurant would be closed.