Traffic has returned to normal northbound on the Hume Highway.

Update at 4.44pm on Monday, September 7:

The crash site has been cleared after an earlier crash between a truck and two cars.

The highway is still affected in a northbound direction.

Motorists are advised to expect delays with heavy traffic in the area.

Update at 4.12pm on Monday, September 7:

A NSW Transport Management Centre spokesman said the Hume Highway was still closed in a northbound direction.

Traffic remains heavy in the area and there is a queue of about 3.5 kilometres.

Update at 4.05pm on Monday, September 7:

A 47-year-old man has been transported to Bowral and District Hospital with minor injuries.

This is according to a NSW Ambulance media spokesman.

Paramedics are treating two people at the scene, including a 54-year-old man with neck and chest injuries and a 56-year-old man with suspected minor injuries.

Update at 3.55pm on Monday, September 7:

Northbound traffic is backed up for about six kilometres.

Motorists are advised to expect heavy traffic conditions and significant delays.

Emergency services and Transport for NSW crews are currently in attendance.

Update at 3.30pm on Monday, September 7:

A HAZMAT pumper vehicle has been dispatched from Fire and Rescue NSW's Goulburn station.

There is no confirmation the truck is required to clean up any chemical spills at this stage.

All northbound lanes are currently closed.

If you are intending on travelling north towards Sydney through Marulan, consider delaying your trip and avoiding the area.

Motorists are also asked to give way and make room for emergency vehicles attending the incident.

Update at 3.10pm on Monday, September 7:

A NSW Ambulance Media spokesman said reports suggested the truck driver sustained injuries in the crash.

The spokesman was unable to confirm any further possible injuries.

Five ambulance crews were called to the crash site at about 2.40pm.

An ambulance helicopter is landing near the highway shortly.

Traffic is heavy in the area. Motorists are advised to exercise caution and reduce their speed.

Initial report at 3pm on Monday, September 7:

Emergency services are en-route to a crash on the Hume Highway near Marulan.

Northbound traffic has been affected on the highway approaching Inverary Road.

A NSW Transport Management Centre spokeswoman said police, NSW Ambulance paramedics, nearby fire brigades and Transport for NSW crews have been dispatched.

The crash happened just before 3pm on Monday, September 7.

Motorists are advised to reduce their speed and exercise caution.