Traffic on the M5 motorway has been backed up for more than 10 kilometres due to the closure of city-bound lanes on the M5.

Transurban, which operates the road, closed the tunnel earlier this morning in order to repair a ventilator fan.

Aerial footage and the Live Traffic website show cars backed up from the closure point near Beverly Hills, all the way to Milperra.

Transport for New South Wales coordinator-general Howard Collins urged drivers to avoid the area as the delays are not expected to be resolved until after the morning peak.

“I’d ask people, if you don’t need to travel in that area, maybe stay at home or do something different and if you do need to travel, take your time, be patient with people,” Mr Collins said.

He said diversions were in place via King Georges Road and Stoney Creek Road, and the M8 is open, but those roads were also heavily congested.

Mr Collins said Transurban crews were at the site working to repair the fan, work which would require a crane.

“It’s the physical nature of this fan, which needs to be removed, does negate anyone using the tunnel,” he said.

“The engineers are all down there, they’re working as hard as they can … but it’s going to take time. 

“Obviously this was an undiscovered fault which they found overnight.”

‘Safe course of action’

General Manager of WestConnex at Transurban, Denise Kelly, told 702 ABC Sydney it was deemed unsafe to wait until this evening to remove the fan.

“That was a question we asked ourselves, and we assessed the safety situation and safety is the priority, and we decided that the safe course of action was to remove it now,” Ms Kelly said.

She declined to commit to blanket toll relief to compensate drivers impacted by the incident, but individual drivers can contact the company to seek a refund.

“There are plenty of people paying tolls all around Sydney this morning and so it wouldn’t be right for some people to be refunded when they weren’t actually inconvenienced,” Ms Kelly said.

She said crews were working towards reopening the tunnel before the afternoon peak.