State Highway 1 is down to one lane after emergency services attended to a truck on fire.

Fire Service communications spokesman Jaron Phillips said they were called to the blaze just south of Taupo about 1.30pm. They weren't aware of any injuries to the driver.

"It's a truck fire but compounding that is a diesel spill from the truck and it's seems to be quite close to the lake," Mr Phillips said.

Three crews from Taupo and Rotorua are at the scene between the East Taupo Arterial and Tawha Rds.

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"The truck lost an axle which led to the fire and when the first crew arrived it was well involved."

The fire has since been extinguished and a specialist fire investigator was heading to the scene, Mr Phillips said.

Police said there is a large backlog of traffic due to the smoke at the scene and expect delays.