Flights in and out of Melbourne's Tullamarine airport were briefly suspended this morning after the air traffic control tower was evacuated due to a fire alarm.

Passengers are experiencing flight delays of at least 30 minutes and at least one Qantas flight to Sydney has already been cancelled.

One announcement in the Qantas domestic terminal informed passengers that while the tower is active again "there's been a lot of confusion" and it "could still be some time" before the flight schedule resumes or returns to normal.

For updates, follow Melbourne Airport on Twitter.