Teens injured in Blacktown crash

Four teenagers seriously injured when their out-of-control car overturned and smashed into the front fence of a Sydney home were heard screaming "I'm gonna die" in the moments after the crash.

Cameron was sleeping in his home on Bungarribee Road in Blacktown when he was woken at 1.40pm to what sounded "like a bomb going off" in his front yard.

Police are investigating whether the teenage boy who was driving the white Peugeot sedan was speeding when the vehicle, carrying three 15-year-olds and a 16-year-old, mounted the gutter, overturned and clipped a power pole before landing in the front yard of Cameron's house.

"No-one in the car would have been eligible for P-plates," Inspector Adam Powderly, from Blacktown Police, said.

Police, Fire and Rescue NSW officers and paramedics were called to the scene and freed a teenage boy who was trapped inside the driver's seat.

The teenagers - two boys, and two girls - all suffered serious injuries and were taken to Westmead Hospital.

Cameron told 2UE Radio that neighbours helped the teenagers in the car while he tried to comfort his wife, mother-in-law and nine-day-old daughter who had been in the home at the time of the crash.

"(The teenagers) were frantically stressed and panicking, and they were wanting to get out - 'I'm trapped, I'm trapped, get me out, I want to go, call an ambulance, I’m gonna die'," he said.

He said it was the second such incident in a month outside his home.

"We had some hooligan d***head come through the lights at 100 miles an hour, he went through the garbage bins, about a month ago," Cameron said.

Inspector Powderly said the car was not reported stolen. He could not confirm a report that the car belonged to the driver's grandmother and that the driver had taken it without her permission.

Inspector Powderly said one of the teenagers had to be cut free from the wreckage.

"There was fairly significant damage to the vehicle. Three of the teenagers were out of the vehicle at the time police arrived, but the last young person had to be cut out," he said.

Four teenagers have been injured in a car crash in Blacktown this morning.

Four teenagers have been injured in a car crash in Blacktown this morning.

Police were investigating whether speed or alcohol was a factor in the crash.

East-bound lanes of Bungarribee Road were closed while police examined the crash scene.

Police are appealing for anyone with information about the crash to contact Blacktown Police via Crime Stoppers on 1800 333 000.