Update two - Gas explosion in Civic

Firefighters are ventilating the McDonalds restuarant after locating the cause of the explosion.

Further monitoring is also underway to ensure there are no further pockets of gas.

Crews have isolated the sprinkler system and residents have been allowed to return to the apartment building.

ActewAGL are also on scene along with ACT Policing.

ACT Fire & Rescue has also called in the Breathing Apparatus Van.

Crews will remain on scene for some time.