Emergency services have been kept busy dealing with crashes around the country

A scene guard has remained in place overnight, at a point where a ute and trailer went off a bridge into the Clutha River in Cromwell.

Police don't know how many people were in the vehicle, and the National Dive Squad will try to retrieve the vehicles today.

One person is in hospital with serious injuries, after a vehicle and motorbike collided on Mangawhai Road north of Auckland yesterday afternoon.

And State Highway One between Picton and Blenheim has been closed overnight, following a crash at Koromiko around 9pm.