Five adults and two children have been taken to hospital after a four-car crash at Blaxland, in the Blue Mountains, on Sunday morning.
Emergency services arrived at the scene on the Great Western Highway about 10.40am.
TRAFFIC: Local diversions underway on the Great Western Highway after an earlier collision at Blaxland. #9News pic.twitter.com/E1YkQ32kKk
— Nine News Sydney (@9NewsSyd) February 5, 2017
FYI Only - The Great Western Highway is Closed at Blaxland in both directions due to a serious accident. Please... https://t.co/WSvrqsK6lo
— Winmalee RFS (@WinmaleeRFS) February 5, 2017
NSW Ambulance paramedics treated a total of 11 of people at the scene.
Police initially reported three adults had been taken to Westmead Hospital in a serious condition, but a hospital spokeswoman has since confirmed that just one female was admitted in a serious condition.
Four adults were taken to Nepean Hospital with minor injuries, including two women aged 32 and 33, and two males, both 37, while two children were taken to Westmead Children's Hospital.
Those who were taken to hospital had suffered a variety of chest, neck, leg and hand injuries.
The Great Western Highway has remained closed in both directions. As of 2.10pm eastbound and westbound traffic have been able to pass the accident site using the highway's open breakdown lane. Traffic is also being diverted onto local roads.
Senior information manager Alf Paranihi said eastbound traffic was backed up 3½ kilometres on the highway. Traffic moving west is backed up 1½ kilometres.
"The traffic situation is now easing, although it is still heavy in the area," he said.
Traffic management services are advising motorists to allow for extra time, as delays continue.
Blue Mountains Local Area Command officers have launched an investigation.