Major Crash detectives are investigating a rollover that seriously injured two people near Pinjarra on Friday.
The single-car crash happened on South Western Highway near Morrell Road, in Fairbridge about 2:30pm.
It’s understood the hatchback rolled onto its roof and trapped a man and woman inside.
Firefighters had to use hydraulic equipment to cut them free from the wreck.
The two were taken, by ambulance, to Royal Perth Hospital with serious life-threatening injuries.
South Western Highway was closed in both directions, between Fairbridge and Del Park Roads, for most of the evening as Major Crash investigators probed the scene.
The RAC Rescue helicopter was deployed to the scene to transport the two but was left grounded after a mechanical issue.
Crews had to wait more than an hour for a mechanic from Perth to give the all clear.
Police confirmed the helicopter was grounded due to a mechanical fault.
A spokesperson from the Department of Fire and Emergency Services and another from St John Ambulance both told Skeer Media they had no knowledge of the mechanical malfunction.
St John Ambulance manages the states two RAC Rescue helicopters.
Emergency services are at the scene of a serious road crash in Fairbridge.
The crash happened on South Western Highway near Morrell Road about 2:30pm.
It’s understood two people were trapped inside a hatchback which had rolled onto its roof.
The two have since been cut free by firefighters and were expected to be flown to Royal Perth Hospital by the RAC Rescue helicopter but have been taken by road instead.
Major Crash investigators are probing the scene.
Drivers should avoid the area.