Two people are in hospital in critical condition after their sedan was T-boned by a police vehicle racing to an urgent job on Sunday.

Emergency services were called to Prairie Vale Rd in Bossley Park — about 45 minutes west of Sydney’s CBD — about 12.20pm following reports of a crash.

WATCH THE VIDEO ABOVE: Two critical after police wagon collision

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Officers were responding under lights and sirens to an incident involving a child seen running on the road, police say, when their vehicle collided with a red Kia sedan. The occupants — a 21-year-old P-plater and her 50-year-old aunt — were just 200m from home on their way to the shops.

The impact was so violent that both vehicles came off the road, crashed through a fence and hit separate houses.

Both women were trapped in the vehicle and unconscious. The driver was treated at the scene before being taken to Westmead Hospital in a critical condition, while her aunt was taken to Liverpool Hospital where she is also critical.

“We couldn’t do anything because the car was squashed,” a witness said. “Yeah, no talking, no crying, just like bleeding.”

Two male police officers were taken to Liverpool Hospital for minor injuries and mandatory testing. No one inside the houses were injured but residents said it was a miracle there wasn’t a third victim.

The occupants of the house struck by the police vehicle told 7NEWS the room where the car landed is their baby son’s bedroom, and that it was only by chance they weren’t home when it happened. Otherwise, the child would have been enjoying his midday nap.

A critical incident has been declared with investigations ongoing.

Two people are in a critical condition. Credit: 7NEWS

Investigations into the incident are ongoing. Credit: 7NEWS