The gas explosion is believed to have occured in the McDonalds restaurant.
Firefighters are still investigating and attempting to shut off the gas.
The seven floor appartment block above the restaurant has also been evacuated.
ACT Fire & Rescue has three pumpers, a commander and the hazardous materials unit on scene.
The ACT Ambulance Service is also in attendence.
One man has been taken to the Canberra Hospital in a serious condition with burns to his body.
No one else is being treated at this stage.