SYDNEY, March 29 (Xinhua) -- Flight services have returned to normal at Sydney Airport on Friday after its air traffic control tower was evacuated shortly before noon.

Airservices Australia, the body which oversees the nation's air traffic control operations, posted to social media platform Twitter that the tower had been "evacuated due to smoke."

With 20 air traffic control staff unable to perform their duties, all flights in and out of Sydney Airport were placed under a "full ground stop."

But after one hour, fire investigators "cleared staff to return."

"When crews arrived they searched the tower and found no sign of fire," New South Wales State Fire and Rescue Superintendent Bryce Jonas told 9news.

"They then used thermal imaging cameras to detect the source of heat causing the smoke, and it came from a battery backup system for the tower's computers that had overheated."

"Crews removed the battery system, took it outside and hit it with a carbon dioxide cylinder."

"After that they let everyone back in, all under an hour. No injuries occurred."

As a result of the delay, airlines have warned travellers that they may experience major delays after planes were diverted and delayed right across the country.

A video posted to social media captures the captain of a Virgin Australia flight explaining the situation to passengers

"Every aircraft that was not in the air has been told to stay on the ground," he said over the plane's speakers.

"People are stuck in Melbourne, Brisbane, Adelaide, you name it."