Officers scramble to safety after police car bursts into flame mid-duty

Four police officers have managed to escape unscathed after the car they were driving caught fire on Sydney's M7 highway.

The specialist officers were on "urgent duty" headed southbound when the Kia Sorrento they were driving broke down at Rooty Hill in Sydney's west about 8.25pm last night.

It is believed the officers were responding to a call of a neighbourly dispute, driving with their lights and sirens on, when the cars engine suffered a major fault.

The officers pulled the car over and escaped the vehicle just as flames emerged from beneath the Sorrento's bonnet, NSW Police reports.

Fire & Rescue NSW attended the scene and extinguished the fire, which forced the closure of the M7 for roughly two hours.

Firefighters also managed to extinguish flames that had leapt to nearby grass and were also forced to shield themselves at one point as explosions came from the boot of the car, believed to have been caused by ammunition stored there.

No one was injured and police believe engine failure may have the cause of the fire.

The vehicle will be towed and examined by experts.