"'I've never seen anything like it," Josiele Rosa Silva Tomas, president of Brumadinho resident's association, said. "It was horrible ... the amount of mud that took over."

Silva Tomas said she was awaiting news of her cousin, and many people she knew were trying to get news of loved ones.

Seven bodies had been recovered by late Friday, according to a statement from the governor's office of Minas Gerais state.

Vale CEO Fabio Schvartsman said he did not know what caused the collapse. About 300 employees were working when it happened. About 100 had been accounted for, and rescue efforts were under way to determine what had happened to the others.

"The principal victims were our own workers," Schvartzman told a news conference Friday evening. He said a restaurant was buried by the mud at lunchtime.