All lanes of the Great Western Highway have now been re-opened following a serious crash at Blackheath this morning [Wednesday].
"Alternating traffic conditions have now been lifted following an extensive clean up operation and the completion of investigations by police," said a Transport Management Centre spokeswoman.
Motorists are still being advised that traffic remains heavy in the area.
An Ambulance NSW spokeswoman said paramedics treated seven patients after being called to the scene of the three-car collision about 8.30am.
Three people were trapped for up to one-and-a-half hours before one was taken by road ambulance to Nepean Hospital. The other two trapped patients were freed and taken by rescue helicopter to Westmead Hospital.
"They're both in a serious but stable condition," she said.
Four other people were assessed at the scene but their minor injuries did not require hospitalisation.