10.25am: Traffic is still heavy on Mount Ousley. 

The NSW Transport Management Centre says delays of about 25 minutes are still being experienced northbound, with traffic queued 4.5km.

10.10am: One of the truck drivers, a 30-year-old man, has been taken to Wollongong Hospital with facial injuries.

Emergency services remain at the scene, where Bulli RFS have mopped up a spillage on the road.

The roadside is littered with debris from the damaged truck.

Two of three lanes remain closed at the accident site and traffic is still heavy in the area. 

Meanwhile, the broken down semi-trailer on Picton Road has been moved and is no longer affecting traffic.

9.45am: Mercury journalist Ang Thompson and photographer Sylvia Liber are caught in heavy traffic on the M1 Princes Motorway. 

9.40am: Motorists heading north from Wollongong are advised to expect delays of about 25 minutes after a two-truck accident on Mount Ousley on Wednesday morning.

Elsewhere, a broken down semi-trailer has closed one of two westbound lanes on Picton Road, about 200 metres west of M1 Princes Motorway.

9am: An accident involving two trucks is causing significant traffic delays on Mount Ousley. 

Two of three northbound lanes on the M1 Princes Motorway have been closed after the accident, which happened about 8.50am on Wednesday. 

The NSW Transport Management Centre says traffic is heavy in the area and motorists can expect significant delays.

Light vehicles can use Bulli Pass as an alternative.

Traffic crews and emergency services are on site.

More to come.