Both lanes of the Stuart Highway have now been blocked for hours leading to long lines of traffic several kilometres long.

Some cars and "light vehicles" are now moving although trucks are not.

There is still no official information on the condition of the two people believed to have been traveling in the car pictured above which collided with a road train just after 4am.

In the latest police update, issued just minutes ago, the highway is expected to be blocked at least partially for some hours yet.

Police say traffic diversions are now in place but motorists should reconsider their plans if they intended to use the Stuart Highway.

The line of waiting cars and trucks stretches several kilometres from a serious crash site near Edith River bridge on the Stuart Highway.

Many drivers had left their stuck vehicles to wait in the shade on the side of the highway.

Some drivers are saying they have been stuck there since 5am.

"It is likely to remain closed for some time. Motorists are advised to delay their plans to travel," police have advised.

A road train and the car collided about 45km north of Katherine near the Edith River bridge.

"The road train is believed to have damaged fuel tanks and to be leaking fuel."

The truck is pulled to the side of the highway several 100 metres from the crashed car.

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