Seventy-five people are now known to have died in the flooding in Brazil’s southern Rio Grande do Sul state, while more than 100 people remain missing, local authorities said on Sunday.

The state’s civil defence authority said 101 people were unaccounted for and more than 80,000 had been displaced after record-breaking floods swept across the state, which borders Uruguay and Argentina.

Brazil’s president, Luiz Inácio Lula da Silva, arrived in Rio Grande do Sul on Sunday, along with most members of his cabinet, to discuss rescue and reconstruction works with local authorities.

Rescue workers are continuing to race against the clock to save people from raging floods and mudslides. Using four-wheel-drive vehicles and at times jetskis, rescuers made their way through waist-deep water, searching for those who had been left stranded by the rising waters.

Video posted online by Lula appeared to show a helicopter dropping a soldier on the roof of a house, and the soldier using a brick to pound a hole in the roof and rescue a baby wrapped in a blanket.

Storms have affected almost two-thirds of the state’s 497 cities, leading to landslides, destroyed roads and collapsed bridges as well as power outages and water cuts. More than a million people lacked access to drinking water, according to Brazil’s civil defence agency.

On Thursday a dam at a hydroelectric plant between the cities of Bento Gonçalves and Cotiporã partly collapsed, while entire cities in the Taquari River valley, such as Lajeado and Estrela, were completely overtaken by water. Helicopters flew continually over the cities as stranded families with children awaited rescue on the rooftops.

One woman said she had never seen anything like it. “It felt like a horror movie,” Isolete Neumann told the Associated Press earlier this week. “People were making barricades in front of hospitals with sand and gravel.”

Last week Lula described the floods as being among the largest Brazil had ever seen. “Never before in the history of Brazil had there been such a quantity of rain in one single location,” he told reporters.

The flooding across the state has surpassed that seen during a deluge in 1941, according to the Brazilian Geological Service. In some cities, water levels were at their highest since record-keeping began almost 150 years ago, the agency added.

In Porto Alegre, Rio Grande do Sul’s capital, the Guaíba River broke its banks, flooding streets. Aerial images showed residential areas in Porto Alegre that were underwater as far as the eye could see, with the tops of some houses barely visible.

Across the city, people stood on rooftops, hoping to be rescued, while others in canoes or small boats navigated streets that have turned into rivers. Porto Alegre’s international airport on Friday suspended all flights for an indefinite period.

Rains were expected to continue in the northern and north-eastern regions of the state, but the volume of precipitation has been declining, and should remain below the levels seen in recent days, according to the state meteorology authority. Earlier in the week in some areas as much as 150mm (6in) of rainfell within 24 hours.

“River water levels should stay high for some days,” the state governor, Eduardo Leite, said on Saturday on social media, adding that it was difficult to determine exactly how long the situation would continue.

Earlier in the week Leite had described the floods as a “critical moment” for the state. “The current event will be the worst climate disaster that our state ever faced,” he wrote on social media on Wednesday.

The state of Rio Grande do Sul sits at a geographical meeting point between tropical and polar atmospheres, giving rise to a weather pattern that includes periods of intense rain and drought. Local scientists say the pattern has been intensifying as a result of the human-made climate crisis.

In September, Rio Grande do Sul was hit by an extratropical cyclone, leading to flooding that killed more than 50 people. The cyclone came after more than two years of persistent drought, during which the region had only scarce showers.

With contribution from Reuters, Agence France-Presse and Associated Press