More than a year's worth of rain fell in a matter of hours Friday, inundating entire neighborhoods of the port city about an eight-hour drive south from Buenos Aires.

Argentines have been particularly shaken by the unknown fate of two little girls who were travelling with their parents when their car became marooned in the fast-rising waters.

A delivery van driver managed to rescue the children and their mother and bring them aboard his vehicle but it too filled with water, relatives of the family told local media.

The four climbed onto the roof of the van but a flood surge ripped away the driver and the girls.

The mother survived, as did the children's father, but the body of the delivery driver was found on Sunday.

The government has ordered three days of national mourning over Bahia Blanca's worst disaster in decades, with about 500 people still in temporary shelter four days after the deluge.

One hundred people remained unaccounted for, but authorities believe most were simply unable to reach out because of damage to the city's cellphone masts and power cuts caused by the floods.

Bahia Blanca's mayor, Federico Susbielles, told reporters Monday that embankments were being built and pumps used to lower the water levels.

He said electricity had been restored to about 70 percent of households across the city of 350,000 people.

- Condolences from Pope, Messi -

The receding waters revealed catastrophic scenes in several neighborhoods Monday of mud-caked streets filled with debris, damaged furniture, and cars that had been tossed about or piled up on each other.

AFPTV images showed overturned cars lying in a gully and residents trying to clear their houses of mud.

There are still "no buses, no banks and if you have to buy something you have to do it in cash because there is no {payment) system," Guillermo Busteros, who lives close to a canal that burst its banks, told AFP.

About 200 firefighters joined the clean-up effort and almost 800 police officers were deployed to prevent looting.

Susbielles said the storm had caused an estimated $400 million in infrastructure damage.

According to provincial security minister Javier Alonso, 23 schools were badly damaged and parts of Bahia Blanca submerged in 1.5 meters (five feet) of mud.

The central government has authorized emergency reconstruction aid of 10 billion pesos ($9.2 million).

Soccer clubs and associations launched campaigns to raise money for the victims.

The Argentine Football Association released a video of national coach Lionel Scaloni calling for donations through the Red Cross.

For his part, Atlanta football club director Simon Oliak said: "We have three rooms filled with dozens of bags of donations."

Argentina's superstar Lionel Messi took to Instagram to wish "much strength to all those who are having a rough time in this difficult moment."

Argentine-born Pope Francis, in hospital with pneumonia, said he felt "close to the suffering" of the victims.

Some two million hectares of farmland in the country's agricultural heartland were damaged.

Environment official Andrea Dufourg said the extreme weather event was "a clear example of climate change."

"Unfortunately this will continue to take place... we have no other option than to prepare cities, educate citizens, establish effective early warning systems," said Dufourg, who is director of environmental policy for Ituzaingo city outside Buenos Aires.

Bahia Blanca has suffered past weather-related disasters, including a 2023 storm that claimed 13 lives.

The governor of Buenos Aires province, Axel Kicillof, described the flooding as "an unprecedented catastrophe."