Hundreds of vehicles have suffered tyre damage after a truck spilled metal debris on one of Australia’s busiest highways.

The M1 on the NSW Central Coast is closed southbound from Wyong Road to Moonee Moonee, a section of motorway almost 30 kilometres long. Northbound lanes remain open.

Dozens of cars remain beside the roadside, with drivers needing to change their tyres.

Chief Inspector Thomas Barnes of Highway Command told 2GB the debacle is “somewhat unprecedented”.

“A number of people are not realising until they’ve arrived at their destination that they’ve also got damaged tyres that are subject to a slow leak,” Barnes said.

He said anyone who had driven down the M1 should inspect their tyres because of the possibility of a slow leak.

The owner of the truck company has apologised for the debacle.

NJ Ashton general manager Daniel Falconer said they weren’t 100 per cent sure how this has happened.

“We’ve been doing this for about three or four years and we’ve never had a problem,” he told 2GB.

“The tins on the back of the truck were locked. We don’t know how it has come out of the back of a truck.”

The driver had “absolutely no idea” the steel fragments were coming out the back of the truck.

Ashton said the driver was “devastated” by what’s happened.

“We’re very, very sorry for what’s happened,” he said.

“We’re doing as much as we possibly can.”

B-Doubles are being parked on the roadside and motorists have been urged to allow for extra travel time.

Anyone who has suffered damage as a result should contact NJ Ashton, with their insurance to cover the costs.