Six people have been injured during two crashes near Huntly, one of them seriously.
Traffic has been backed up on State Highway One for 14 kms.
A woman was initially trapped, and is now being treated at the scene while awaiting transportation by rescue helicopter to Hamilton.
Two other people have suffered moderate injuries, and two children suffered minor injuries.
One person was also treated for a moderate injury, believed to be a broken arm, following the initial crash.
A minivan and a bus are believed to have collided on Ralph Road, which was a diversion from an earlier crash.
There was a three-car pile-up on State Highway One near East Mine Road about 10am.
The site of the original crash was cleared up about 11am, but the backlog of traffic will still take some time to clear.
Police ask motorists to remain patient and take care as traffic clears.