The incident took place at a popular tourist attraction

    At least six people were killed and dozens injured after a massive rock formation collapsed on top of three boats in Brazil in an incident that was captured on video and posted on social media. 

    Brazilian authorities have confirmed the incident, which happened in the city of Capitolia in the Brazilian state of Minas Gerais on Saturday at Furnas Lake, according to the New York Daily News. 

    As many as 20 people may be missing and officials are working to identify them, Edgard Estevo, commander of the Minas Gerais State Fire Department, said in a news conference. He said many of the injured had been released from the hospital by Saturday night.

    In the video posted on Twitter, a large portion of a cliff can be seen crashing into the water at a popular tourist attraction along the Rio Grande river, directly on top of several boats as horrified onlookers screamed. Furnas Lake was created in 1958 in conjunction with the development of a hydroelectric plant. 

    Estevo said the accident occurred between the towns of Sao Jose da Barra and Capitolio, from which the boats had left.

    The Brazilian news portal G1 reports that firefighters believe a sudden downpour of rain caused the rocks to become dislocated and fall into the river. Helicopters and divers were deployed to help with the search and rescue.

(Adapted from https://www.foxnews.com/world/2-dead-at-least-15-injured-after-massive-brazil-rock-formation-collapses-onto-boats)

Choose the alternative that correctly substitutes may in the sentence “As many as 20 people may be missing and officials are working to identify them”. (paragraph 3).