A large truck and trailer fire on the Waikato Expressway is blocking traffic heading south

Four fire and emergency crews are currently battling the blaze, three kilometres south of Rangiriri.

There are no reports of injuries, and a police say while the truck and trailer is on the shoulder the fire is stretching across the road.

A witness who was turned around by police, Wayne Stockman, says he could see the fire glowing in the sky from about 300 metres away.

He says he could see a large truck on the side of the road fully engulfed in flames.

Stockman says there was a fire truck in attendance but that was doing little to bring the blaze under control.