One person is reported to be critically injured following a crash in the Waikato.

Emergency services are responding to a serious crash on Ouruwhero Road near Ōtorohanga.

Police were advised at 7.10am that a car had crashed on a bridge, between Kakamutu Road and Kio Kio Station Road, blocking both lanes of the bridge.

"The driver is reported to be critically injured," says a police spokesperson.

"Traffic management is being put in place.

"Motorists are asked to avoid the area or take alternative routes where possible."