High-voltage power lines have come down across one of Melbourne’s busiest freeways, causing headaches for commuters heading to the airport and the city.

VicRoads have closed the Tullamarine Freeway inbound at Bulla Rd and outbound at Moreland Rd.

Chris Miller from VicRoads Traffic Control told Tony Jones existing traffic will be diverted.

“It looks like we’re going to have to close the Tullamarine Freeway, we’ve got high voltage power lines down right across the outbound lanes at Moreland Road,” Chris said.

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All traffic is stopped with emergency services to begin diverting cars off the freeway and back on after Moreland Rd towards the airport.

Witness Eli told Tony Jones a semi-trailer is to blame for bringing down the power lines.

“Looks like a semi’s pulled them down and the cord is just hanging off the bridge and cars are just driving over the top of live wire,” he said.

The freeway is expected to be closed for some hours.

Some motorists have been stuck for around 45 minutes.