At least seven people were killed and three were missing after a cliff collapsed onto boats carrying tourists on a lake in Brazil, authorities said Saturday.

Rescue teams including a dive squad and members of the Brazilian Navy rushed to Furnas Lake in Minas Gerais state, where panicked tourists had watched helplessly as a large rock fragment broke off a ravine and plunged atop three boats.

The latest official toll is "seven dead and three missing," Minas Gerais firefighters' spokesman Pedro Aihara said on Saturday night.

Another 32 were wounded, including nine who had to be hospitalized, authorities said. 

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Firefighters had initially reported 20 missing, but "that number was substantially reduced because a good part of the victims who were unaccounted for were people who moved by their own means to hospitals," Aihara said in a voice message sent to reporters.

Tourists flock to see the rock walls, caverns and waterfalls that surround the green waters of Lake Furnas, formed by the hydroelectric dam of the same name.

Dramatic videos shared on social networks caught the exact moment when the cliff fell on the three boats. 

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Another video posted on social media shows the minute before the fall, in which several people warn that "lots of stones are falling" and yell at the occupants of the other boats to move away from the wall. 

President Jair Bolsonaro retweeted some of these videos on his account, and reported that "as soon as the unfortunate disaster occurred, the Brazilian Navy moved to the site to rescue victims and transport the injured."

The divers' search will be interrupted overnight for safety reasons and resumed in the morning, but other rescuers continue to work at the site.

Very heavy rain has fallen in recent days in southeastern Brazil, making the collapse more likely, according to firefighters.