State Highway 25, at the intersection of Banks St in Thames is closed for several hours while emergency services respond to a crash involving a car and a motorcycle.

Northbound traffic on State Highway 25 is being turned back at Kopu and southbound traffic is being turned back in Thames, police said.

Police were notified of the accident at 11.55am.

One person was reported to be in a critical condition.

The road was expected to be closed for several hours, and motorists were advised to avoid the area and expect delays.

The Serious Crash Unit was in attendance.