Melbourne trams resume after explosion

Tram services along a busy Melbourne road have resumed after an explosion occurred when live power lines struck a carriage.

The explosion startled about 30 passengers who evacuated the tram about 9.30am.

A Metropolitan Fire Brigade confirmed overhead wires sparked a small fire on top of a St Kilda Road tram at the corner of Toorak Road.

"About 30 people on board were evacuated, and we believe there are no injuries," he told AAP.

A witness, Kate, told 3AW she heard two large explosions and saw fire and smoke coming from the tram.

"I heard this massive bang ... people were trying to get off and it exploded again," she said.

Yarra Trams said they are investigating a potential fault with the tram, which could have caused the damage to the overhead wire and thanked passengers for their patience.

Eight busy tram routes were shut down for about three hours and replacement buses continue to help deal with the backlog.

"We understand the effect that incidents like this can have on our passengers, and we appreciate their patience while our crews worked to safely restore services," a spokesman said.