Authorities are searching for 99 unaccounted people after part of a 12-storey beachfront building collapsed in a town near Miami.

At least one person died after a huge section of the building was reduced to rubble after it crashed to the ground around 1.30am on Thursday local time (6.30am UK time).

The number of people unaccounted for was updated by police and Miami-Dade mayor Daniella Levine Cava after officials initially said 51 people were missing.

Ms Levine Cava also said 102 people are accounted for and safe.

The search continues for survivors in the rubble at Champlain Towers South in the town of Surfside, Florida but officials do not know how many were inside when it fell.

“The building is literally pancaked,” Surfside Mayor Charles Burkett said. “That is heartbreaking because it doesn’t mean, to me, that we are going to be as successful as we wanted to be in finding people alive.”

A British mother and relatives of Paraguay’s first lady are among around a dozen confirmed to be missing in the disaster.

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A relative of Bhavna Patel, a 38-year-old British and US citizen, confirmed to Sky News that she, her 42-year-old husband Vishal Patel, and their one-year-old daughter Aishani Patel are yet to be found.

Paraguayan Foreign Minister Euclides Acevedo told local media that six people from the South American country are still unaccounted for after the collapse.

They are Sophia López Moreira, the sister of first lady Silvana Abdo, her husband Luis Pettengill, her three children and the family’s assistant, according to Paraguayan authorities.

Gilmer Moreira, press director of Paraguay’s presidential palace, told the Associated Press the first lady is planning to travel to the states with her husband President Mario Abdo.

A family of three from Colombia are also missing and are feared to have been in the apartment block.

Luis Fernando Barth Gomez, his wife Catalina Barth Gomez and their 14-year-old daughter Valeria Barth Gomez were staying on the second floor of the building, a family spokesperson told NBC News.

Valeria was attending a tennis camp in South Florida. The family were last heard from at 8pm local time on Wednesday.

Florida Senator Marco Rubio tweeted that almost a third of the missing are foreigners, and that he is working with the consulates of different Latin American countries to help some of the families get US visas.

Nine people from Argentina, six from Colombia, four from Venezuela and three from Uruguay, are missing according to officials in those countries.

Maria Obias-Bonnefoy, 70, from the Philippines and Claudio Bonnefoy, 86, from Chile are were confirmed missing by a family member.

Both lived on the 10th floor in unit 1001 of the Surfside building that collapsed, meanwhile a cousin of Miriam and Arnie Notkin said they haven’t been found.

Teams of 10 to 12 rescuers have been sifting through the wreckage for survivors since the incident.

Earlier, rescuers saved a mother and child, but the woman’s leg had to be amputated to remove her from the rubble, Frank Rollason, director of Miami-Dade emergency management, told the Miami Herald.

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Emergency crews rush to collapsed building

Rescuers pulled at least 35 people from the rubble by mid-morning, and heavy equipment was being brought in to help stabilise the structure to provide more access, Raide Jadallah of Miami-Dade Fire and Rescue said.

Florida representative Debbie Wasserman Schultz said the incident was a “tragedy without precedent”, while Florida governor Ron DeSantis, who toured the scene, said television did not capture the scale of what happened.

Rescue crews are “doing everything they can to save lives… that is ongoing, and they’re not going to rest,” he added.

Authorities did not say what may have caused the collapse which affected around half of the building’s 130 units.

On video footage captured from nearby, the centre of the building appeared to fall first, with a section nearest the ocean teetering and coming down seconds later as a huge dust cloud swallowed the neighbourhood.

President Joe Biden promised to provide federal aid and hotels have opened to some displaced residents.

Champlain Towers South was built in 1981 and has more than 100 residential units, according to NBC News.

It had a few two-bedroom units currently on the market, with asking prices of $600,000 (£430,000) to $700,000 (£502,000).

The building is located across from a beach in the oceanfront community of about 6,000 people and police blocked nearby roads and traffic was being diverted on Thursday.