A teenager has died and three are in a critical condition following a two-vehicle crash near Morongla on Friday afternoon.
About 12.30pm, emergency services responded to reports of a crash on Lachlan Valley Way, about 20km south of Cowra.
On arrival, officers attached to Chifley Police District and NSW Ambulance Paramedics were told a 4WD, with a caravan attached, and a sedan, had collided.
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Seven ambulance crews and three specialist medical team via helicopter were dispatched to the scene.
Despite the efforts of emergency services, the 18-year-old female driver of the sedan died at the scene.
Inspector Peter Rowlands with NSW Ambulance said it was a "devastating scene".
"Multiple patients with critical injuries can create a very challenging environment for paramedics," Inspector Rowlands said.
"It's been a horrible week on our regional roads.
"We urge the public to take care when travelling around the state."
Her 18-year-old male passenger was airlifted to Canberra Hospital in a critical condition.
The driver of the 4WD, a 78-year-old man, and a passenger, an 80-year-old woman, were also airlifted to Canberra Hospital in a critical condition.
Lachlan Valley Way remains closed in both directions and police are urging motorists to avoid the area.
Diversions have been put in place, with northbound traffic from Boorowa to use Murringo Rd, Olympic Hwy to Cowra via Young.
Southbound motorists are diverted at Morongla Rd, Olympic Hwy, Murringo Road to re-join Lachlan Valley Way at Boorowa via Young.
Officers from the Traffic and Highway Patrol Crash Investigation Unit are on scene and have commenced an investigation into the circumstances of the crash.
Inquiries are continuing.