Traffic on the Great Western Highway is being affected in both directions by a crash that occurred just before 4pm.
The crash, involving two cars, occurred at Marrangaroo, five minutes west of Lithgow, between Reserve Road and Hughes Lane.
At least one person is believed to be trapped and emergency services, including the Volunteer Rescue Association, are in attendance.
People travelling in the area have been urged to exercise caution and leave extra travel time.
There are no further details on the condition of the vehicles' occupants.
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