Four passengers and the driver had to flee a tram overnight as it burst into flames in Melbourne’s CBD.

The fire started in the tram’s undercarriage while it was at the intersection of Swanston and La Trobe streets around midnight.

No one was injured.

MFB Commander Shane Rhodes says the cause of the fire is under investigation.

“MFB appliances and crews got on scene and proceeded to extinguish the fire and awaited the arrival of tram (officials) to confirm that the power has been isolated,” he said.

“Then they were able to go in and fully extinguish the fire.”