Police believe a van which plunged off a bridge into Tauranga Harbour last night, killing the driver, had been hit by a car which crossed the centre line.

Four people were injured in the three-car crash on the Maungatapu Bridge and a police officer suffered hypothermia when he jumped into the water to rescue the van's 23-year-old passenger.

The officer and the passenger were taken to Tauranga Hospital.

Police said early indications suggested a Mitsubishi travelling east towards Mount Maunganui had drifted across the centre line and hit the van travelling in the opposite direction.

The van left the bridge and plunged to the bottom of the 5m-deep water while the Mitsubishi spun. Another car, which had been travelling behind, then struck the Mitsubishi.

The male driver of the Mitsubishi and a man and woman from the third vehicle were taken to hospital with minor to moderate injuries.

The body of the driver was this afternoon found by police divers inside the submerged vehicle, which was later winched out by crane while local Maori performed a blessing.

Police still wanted to hear from any witnesses who had not been interviewed yet.

Inspector Clifford Paxton said police were "very, very proud'' of the officer who stripped down to his underwear and dived into cold water to rescue the van's passenger

The man had disappeared under the water but when he re-surfaced the officer grabbed hold of him and they were carried by the current.

The officer managed to calm the man down and turn him onto his back.

After about half an hour focusing on flashlights being used by searchers on the shore, the officer managed to get them both to land.

They were taken to hospital with hypothermia. The police officer was discharged last night and was resting at home today.

"We are very, very proud of the officer's efforts; what he did was pretty outstanding,'' Mr Paxton said.

"He evaluated the situation, believed he could make a difference, and clearly he did make a difference. I have already had members of the public call me this morning to pass on their congratulations.''

The Maungatapu Bridge, which was cordoned off for much of the day, is now open to traffic.

Anyone with any information about the crash was asked to contact Tauranga police on (07) 577 4300.

- APNZ