Cars are seen in a flooded street during heavy rainfall in Auckland, New Zealand January 27, 2023, in this screen grab obtained from a social media video. @MonteChristoNZ/via REUTERS/File Photo

An area flooded during heavy rainfall is seen in Auckland, New Zealand January 27, 2023, in this screen grab obtained from a social media video. @MonteChristoNZ/via REUTERS

Jan 28 (Reuters) - Authorities in New Zealand's biggest city, Auckland, began mopping up on Saturday after torrential rains brought flash flooding and evacuations, with at least two people confirmed dead and two missing in the widespread inundation.

A state of emergency remained in place in the city of 1.6 million people on New Zealand's north island as the rains eased after Friday's flooding in the north, northwest and west.

Prime Minister Chris Hipkins, less than a week in office, flew by helicopter over the city before touring flood-hit homes.

"The level of devastation in some areas is considerable," Hipkins told reporters, describing the event as "unprecedented" in recent memory.

Daylight revealed the impact of the storm, caused by warm air descending from the tropics, sparking heavy rain and thunderstorms, said Auckland Emergency Management, part of the city's council.

"Auckland was clobbered on Friday – Auckland's wettest day on record – and today we start the clean-up," the agency's duty controller, Andrew Clark, said in a statement, urging caution for residents returning home to survey flood damage.

Two men were found dead, New Zealand Police said. A search was under way for a man believed swept away, while another person was unaccounted for after a landslide hit a house in an inner Auckland suburb, police said.

More than 2,000 calls for assistance and 70 evacuations had been made around the city, the New Zealand Herald reported.

City rainfall records were broken, with Auckland Airport logging 249 mm (9.8 inches) in the 24 hours to 9 a.m. on Saturday, beating the 1985 high of 161.8 mm.

Some local flights resumed at Auckland Airport, which had closed domestic and international operations on Friday.

Air New Zealand said its domestic flights in and out of Auckland resumed from noon (2300 GMT on Friday), and international flights out of Auckland would resume from noon on Sunday (2300 GMT on Saturday).

The airport's website said its international terminal was to open for departures from 5 p.m. (0400 GMT), while international arrivals would restart at 4:30 a.m on Sunday (1530 GMT on Saturday).

Air New Zealand said 12 of its international flights due into Auckland had been diverted overnight.

While heavy rain had eased, another period of downpours was possible on Sunday, the national weather forecaster said, adding the impact was "expected to be severe and wide reaching because of the saturated ground".

"More flooding will occur through many northern regions in the coming days," it warned.

On Friday, social media showed firefighters, police and defence force staff rescuing stranded people from flooded homes using ropes and rescue boats.

The flooding forced cancellations of British pop star Elton John's concerts in the city, which had been scheduled for Friday and Saturday nights.