Argentina have declared three days of national mourning after devastating flash floods killed at least 52 people and forced 1,500 residents to evacuate the city of La Plata.
Some people drowned after being trapped in their cars or while walking along city streets when the water rose suddenly on Tuesday night, while others were electrocuted, provincial governor Daniel Scioli told reporters on Wednesday.
Six deaths were reported a day earlier in Buenos Aires, 60km northwest of La Plata.
Many people climbed onto their roofs in the pouring rain after storm sewers backed up. Water surged up through drains in their kitchen and bathroom floors, and then poured in over their windowsills.
"It started to rain really hard in the evening, and began to flood," said Augustina Garcia Orsi, a 25-year-old student. "I panicked. In two seconds, I was up to my knees in water. It came up through the drains - I couldn't do anything."
Local media said between 300 and 400 millimetres of rain fell in just two hours, flooding low-lying neighbourhoods in La Plata and surrounding areas.
President Cristina Kirchner, who grew up near La Plata, visited the flood zone and promised to send more police to calm people's fears that evacuated homes could be looted.
Kirchner spent much of her childhood in La Plata, and her mother, Ofelia Wilhelm, still lives in the same two-storey home here where the president grew up.
"Mom has lost her power and gas but she does not want to leave her home because the water is close to the door, and she is afraid it might start raining again," Kirchner told reporters.
Authorities said around 2,500 people are still unable to return home as they wait for flood waters to subside, and have taken refuge in emergency shelters.
About 100 millimetres more of rain were expected before the bad weather passes on Thursday, the national weather service said.