A plane carrying almost 150 passengers has made an emergency landing at Melbourne Airport after smoke was detected onboard.

Emergency services were called to the airport on Tuesday morning after the captain of the Rex flight from Sydney flagged the problem: Smoke in an onboard toilet cubicle.

More than a dozen fire and other emergency services vehicles responded to the alarm from the incoming Rex 737-800.

A spokesperson for the airline later said the plane landed safely and passengers alighted normally.

“Rex Flight ZL31, operating Sydney to Melbourne, landed safely late this morning after smoke was reported in the aft lavatory. As an abundance of caution, the captain declared an emergency,” the spokesperson said.

Melbourne Airport also confirmed the incident.

“As per Melbourne Airport Emergency Plan, emergency services were activated and attended,” a spokesperson said.

“The plane landed without incident and taxied to the bay. Emergency services are now in the process of standing down.”

Engineers later identified the cause of the smoke and the aircraft resumed operations.

-with AAP