Canberra airport control tower scare ends

Operations into Canberra Airport have returned to normal following the evacuation of the air traffic control tower, after maintenance workers suspected they had found asbestos.

At least two planes flying to Canberra were turned around before the all-clear was given.

Airservices Australia confirmed testing had revealed it wasn't asbestos and air traffic controllers were returned to the tower.

The aviation watchdog said alternative control services had been put in place during the disruption.

Passengers in Brisbane and Sydney took to Twitter to question why their flights had been suspended.

Airservices Australia did not confirm what the substance was.