Three burnt in gas fire in Sydney south

Two kitchen workers and a refrigeration mechanic have suffered burns after a gas explosion in a restaurant in Sydney's south.

Crews were called to the restaurant in Woronora just after midday on Wednesday, where the gas-cylinder fire occurred.

The three injured people were treated at the scene by paramedics and two have been transferred to hospital.

Authorities evacuated seven people from the premises and crews remain on the scene ventilating the building.