Police divers will today search for two people missing after a car drove into a Christchurch lake.

A scene guard remains in place at a carpark on Westlake Dr in the western suburb of Halswell.

The Police National Dive Team was due to arrive this morning to look for the pair who remain unaccounted for after the car disappeared into the former quarry lake.

Earlier attempts to locate the couple were unsuccessful with a diver indicating it was too deep to reach the car.

Police staff and other emergency services remained in the area and in the lake last night, working to establish what happened and speaking to people who saw the tragedy unfold.

Witness Jordan Fleming said he was walking his dog past the Westlake Reserve when he saw a woman in a red hatchback in the car park, and a man outside trying to open the driver's door.

"I heard the accelerator go and that's when the car went off the bank down the hill into the lake," he said.

The man jumped in and swam after the sinking car, diving and resurfacing several times, Fleming said. Then he dived and did not reappear.

Police were called at 5.45pm to reports that a vehicle was submerged in the lake.

Both firefighters and police attempted to dive down to the vehicle to see if anyone was trapped inside. 

Other witnesses said two other people who tried to save the pair were taken away by ambulance.

A diver went into the lake but came up indicating he could not reach the vehicle, locals say.

The lake sits in the middle of a housing development in Halswell. Residents say it's a deep former shingle quarry popular with runners, walkers, cyclists and children feeding ducks.