Four remain critical after NSW fiery smash

A critically-injured man could face charges over a fiery eight-vehicle crash that killed a teenage Uber passenger in Sydney's southwest and left three others fighting for life in hospital.

Police believe a 26-year-old man was speeding in his blue Commodore before it veered into oncoming traffic on Friday evening at Woodbine causing the "unbelievable" smash that impacted seven other vehicles.

A 17-year-old passenger travelling in an Uber was killed and five others were taken to hospital.

The 26-year-old's vehicle caught fire as a result of the crash and he's now in an induced coma at Liverpool Hospital after undergoing surgery, a police spokeswoman told AAP on Saturday.

It's reported he was speeding before the crash and didn't have his lights on despite the incident occurring at 7.15pm.

"He could be looking at a number of serious traffic and criminal offences," Assistant Commissioner Michael Corboy told reporters in Sydney, adding the scene was "unbelievable".

"In the end, there could have been a lot more people killed. It could have been a scene of utter devastation."

Four people remain in a critical condition in Liverpool Hospital including the 26-year-old blamed for the smash, a hospital spokeswoman told AAP late on Saturday.

The others - two men aged 17 and 20 and an 18-year-old woman - were also passengers in the Uber. The 57-year-old Uber driver was less seriously injured.

"In the ride-share vehicle they obviously all knew each other," Mr Corboy said.

"Those people have now lost either a friend or relative and we have to knock on people's doors."

Another man in his mid-50s remains in a stable condition at Campbelltown Hospital. He's expected to be discharged later on Saturday night.