A section of the Pokeno on-ramp on SH2 in north Waikato will remain closed until midnight after a cattle truck crash.

Cows were reportedly running wild on the motorway after a cattle truck rolled at the bottom of the Bombay Hills this afternoon.

Police, fire and ambulance crews and Auckland Council animal control staff were called to the SH2 on-ramp, northbound, at Pokeno, at 1.48pm.

"Initial reports were that cattle were all over the place," fire service spokesman Jaron Phillips said.

Phillips said some cattle had died at the scene, some were trapped in the truck's trailer and others were running over the road.

A fire crew as well as the Fire Service's technical rescue team, which carries rescue equipment such as the jaws of life, were at the scene trying to capture and rescue cattle.

A police spokesman said several cows were killed when the trailer rolled and others had to be put down. The driver of the truck was not hurt and no other vehicles were involved, Phillips said.

He said the animals that escaped were recaptured and hearded to a paddock.

The truck then had to be moved and the road repaired.

NZTA said diversions were in place before Pokeno and would be in place until late tonight.

Motorists should take the southbound off ramp onto SH1, exit at Pokeno and then get back onto SH1 via the Pokeno northbound on ramp to continue north.

SH1 traffic travelling north and south past Pokeno in either direction is not affected by the on-ramp closure.

- © Fairfax NZ News