At least two planes flying to Canberra have been turned around following the evacuation of the national capital’s air traffic control tower, after maintenance workers found asbestos.

Airservices Australia confirmed the tower at Canberra Airport was evacuated on Wednesday after asbestos was found in a piece of equipment.

The aviation watchdog would not confirm when the workers would be allowed to return to the tower but said alternative control services have been put in place.

A Qantas spokesman said the airline was aware of the situation and was assessing what impact, if any, it would have on flights.

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

-AAP