Vic restaurant blaze under control

A large fire in a Melbourne seafood restaurant has been stopped before it could spread to surrounding buildings.

About 15 fire crews are continuing to damp down the blaze, which was broke out about 7.30am and took almost two hours to bring under control.

There is significant damage to the Fu Long Seafood Restaurant, in Box Hill on the Maroondah Hwy, and the cause is unknown.

Fighting the fire was complicated by limited access to the site.

"The fire started out the back in the roof space and the crews have managed to contain it to where it started," a Metropolitan Fire Brigade spokesman told AAP.

"While it put up a lot of smoke, fortunately it did not spread to other shops and structures."

All lanes of the highway were closed at the peak of the fire.

Inbound lanes remain closed and traffic diversions are in place.