A man is dead after a van crashed into a bridge and veered into a water race in Canterbury this morning.

Police said the brown Toyota Hi ace was travelling south on Arundel Rakaia Rd when it left the road near the intersection of Prices Rd.

"The van was airborne for a short time and has then dropped several meters into the water race below."

The man's body was found in the submerged van. It was not thought anyone else was involved in the crash.

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The waterway is locally known as the Rangitata Diversion Race.

Police are in the process of notifying next of kin and the police serious crash unit is investigating.

Elsewhere in the country, State Highway 1 was closed near Taupo after a crash in which a cyclist was killed.

The New Zealand Transport Agency (NZTA) said the crash happened near the Taupo bypass intersection with Broadlands Rd.

The road was expected to be closed for two hours and a diversion was in place through central Taupo.

NZTA is asking motorists to avoid travelling through the area if they can or expect delays.

Traffic was also heavily congested on the southbound lane of Auckland's Southern Motorway after a bus caught fire under the Greenlane interchange.

Read more: Bus fire at Greenlane

Emergency services were called to the bus fire shortly after 10am.

Jaron Phillips from the Fire Service said all passengers had got off the bus safely and there were no reports of injuries.​