UPDATED 5 pm: NSW Police said one man died at the scene of the collision on the Monaro Highway this afternoon while a woman has been taken to Canberra Hospital.
The woman is in a stable condition and suffered only minor injuries.
Officers from the Monaro Police District attended the scene of the crash just after 2 pm this afternoon where they found a truck and a car had collided.
The driver of the truck has also been taken to hospital for mandatory testing.
Correction: An earlier version of this article stated the collision had involved three vehicles.
4 pm: NSW Police have confirmed one person has died following a two-vehicle collision on the Monaro Highway, just south of the ACT this afternoon.
A truck and a car collided near Michelago just north of Kelly Road.
All lanes in both directions at Williamsdale are now closed as emergency services attend the scene.
Motorists are advised to avoid the area and delay their trip.
Southbound light vehicles already in the area are being diverted onto Old Cooma Road. Northbound vehicles are being turned around at Michelago. Heavy vehicles are being parked.
The road is expected to remain closed for a significant time.