Two "good samaritans" helped rescue a woman from the Waikato River after the car she was travelling in plunged into the river, killing its driver, this afternoon.

Emergency services were called to Riverbank Rd, Mercer, near Roose Rd, at about 1.30pm after the car went into the river.

A passenger managed escape from the car, and was then helped to the shoreline of the river by two Asian men. But the driver was unable to get out of vehicle. The car drifted about 150 metres before sinking below the surface.

Senior Sergeant Mark Chivers of Counties Manukau police said officers wanted to hear from the two Asian men who helped save the car's passenger.


The men had left the scene by the time police arrived. Their approximate ages were not known.

As police appeal for the men to come forward, divers are making their way to Auckland to help for the search of the body of the driver of the car.

The police divers are flying up from Wellington and were expected at the scene by 8pm.

Lights by the river would allow them to continue to search after dark, Mr Chivers said.

He said it was too early to say what caused the car to crash into the river.

An earlier statement from police said officers had used a boat to help stabilise the car.

The Police serious crash unit will be investigating.

A man working at the local Mobil service station, Taylor Puru, said a man ran from the site of the accident to the forecourt looking for help.

"He asked this guy with a boat on his trailer to come over to the river. He was in a real rush."

Mr Puru said he could see a lot of police cars and two ambulances, and a fire engine had been and gone.

"There is heaps of cars parked along the street and the police have blocked it off."

Witnesses said they understood a woman had freed herself from the vehicle while the male driver was unable to.

"I was told it might have been a heart attack," said one woman who wished not to be named.

She said there was grey "car wreckage" along the side of the river where rescuers were working.

"There is bits of car everywhere."

She said that section of the river goes from shallow to deep quite quickly and the stretch of road was a common thoroughfare.

She did not believe it was local residents involved, she said.