UPDATE: NSW Police have confirmed one person has died.
A Ford Falcon sedan collided with a Toyota Camry, heading southbound, before it hit an oncoming utility, which then collided with a sedan.
The utility caught fire and the male driver suffered critical injuries, he died at the scene and is yet to be formally identified.
The driver of the Falcon sedan, a man, suffered injuries to his arm and was taken to John Hunter Hospital. He will undergo mandatory testing.
The drivers of the other two vehicles will also undergo mandatory testing.
Their ages are not yet known.
Anyone who witnessed the crash or has dashcam vision of the incident is urged to come forward.
EARLIER: The Westpac Rescue Helicopter has arrived on scene at Stockton, after reports of a serious crash on the northern side of the Stockton Bridge.
Emergency services were called to the scene shortly before 4pm.
It’s understood three vehicles have been involved in a fiery crash on Nelson Bay Road and Fullerton Street, with three patients involved.
An Ambulance NSW spokesperson says a 45-year-old man has serious burns, a 35-year-old man was trapped in the vehicle with a broken arm but in a stable condition, and a third patient was also receiving treatment, in an unknown condition.
KOORAGANG | #FRNSW crews are on the scene following a multi-vehicle crash on Stockton Bridge on Nelson Bay Rd. Two vehicles on fire have been extinguished by firefighters. Exercise caution and allow extra travel time.
STOCKTON: Diversions are in place with Nelson Bay Rd closed in both directions at Fullerton St due to a multi-vehicle crash. Southbound traffic can use Cabbage Tree Rd, while northbound motorists should use the Pacific Hwy and Tomago Rd. Allow plenty of extra travel time.
— Live Traffic NSW (@LiveTrafficNSW) August 21, 2018
THIS STORY IS DEVELOPING, THIS ARTICLE WILL UPDATE WHEN NEW INFORMATION COMES IN.