UPDATE 11AM: Rescue operations are underway to retrieve the driver and submerged van that crashed off the Maungatapu causeway overnight.

The highway is now closed and will remain closed until at least 2pm. Diversions are in place around the city via Hewletts Road and Welcome Bay, depending on direction of travel.

Tauranga harbourmaster is on site at Maungatapu Bridge where a van is submerged in water.

Police undertake a scene examination on the Maungatapu causeway.

A McLeod crane waits on the bridge to retrieve the van.

The police dive squad, harbourmaster and tow truck are onsite to attempt to retrieve the van that crashed off the centre of a bridge following a three vehicle crash at 6.10pm last night.

Divers are searching for the driver, a man in his 20s, believed to be still inside the van that ploughed through the railings into the harbour on the Welcome Bay side.

Police say the van remains submerged in the water, which at low tide is about five metres deep.

A 23-year-old man, who escaped from the submerged vehicle, was taken to Tauranga Hospital with suspected hypothermia along with a police officer who jumped in the water to help him.

The 53-year-old police constable arrived at the scene to find the passenger in distress in the water and stripped down to his underwear before jumping in the water.

WBOP police communications manager Kim Perks says the constable reached the man and they both went underwater.

'The officer managed to keep hold of the man as the current took them and pull him on to his back.

'He saw flashlights on the shore from other police members searching and focused on moving towards those lights.”

Two cars were left on the bridge last night.

After about 20 minutes the officer managed to get the man to shore and both were taken to Tauranga Hospital suffering from hypothermia. Both have since been discharged.

A 30-year-old woman and 31-year-old man from one of the other vehicles and a 45-year-old man, who was the sole occupant of another vehicle, were also taken to hospital with moderate injuries.

Bay of Plenty District Health Board communications manager Diana Marriott says the 45-year-old man remains in hospital with moderate injuries.

'He is in a comfortable condition. The rest of the people brought in last night were discharged from hospital overnight.”

Two cars blocked the highway last night – one in the northbound lane and another crashed at a 45 degree angle into it. The roof of one of the vehicles was removed as emergency services worked last night to clear patients from the scene.

It is not known how the accident occurred but witnesses report one of the cars crossed the centreline crashing into another vehicle heading in the opposite direction.

Firefighters from Tauranga and Greerton were called to the scene.

Tauranga Fire Brigade senior station officer Nigel Liddicoat says firefighters removed the roof of one of the cars on the bridge to free a person inside.

'We just basically took control of the extraction. The police and Coastguard searched the waters for the remaining vehicle.

'Once firefighters removed the patient from the car, they assisted at the scene where they were needed.”

Firefighters provided an emergency lighting plant with generator to help in the dark search.

The Tauranga-based TECT TrustPower rescue helicopter was called in and searched the waters surrounding the bridge for the van.

Police and other emergency services remain at the scene this morning.

Diversions:

Motorists are advised to use alternative routes to and from Mount Maunganui and Papamoa as State Highway 29 near the Maungatapu Bridge is closed, says the NZ Transport Agency.

Drivers are advised they can use the following detour options:

To and from Mount Maunganui:

• Hewletts Road and across the Harbour Bridge

To and from Papamoa and Te Puke:

• State Highway 2, Welcome Bay Road and State Highway 29.

The Transport Agency says it is unknown at this stage how long this section of highway will be closed, the agency says it will provide a update once the road is reopened.

Lifeguards provide support.