Emergency crews are battling to contain a major fire that has broken out in a Tekapo restaurant.

Fire and Emergency New Zealand (Fenz) southern communications shift manager Andrew Norris said they received a call at about 1pm about a fire at the Lake Tekapo Tavern and Reflections Restaurant.

When crews arrived the fire was "well involved", he said.

He said the blaze is now contained - and they're dampening down the site.

The building is 600 square metres, and more than half of it has been severely damaged.

A fire investigator is now at the scene.

He was unsure if the restaurant had been open at the time but it had been evacuated by the time they arrived. There were no injuries reported.