At least 18 inmates died in clashes in two separate penitentiaries in Brazil’s Amazon region and more than three dozen escaped after a third prison riot caused a large fire in a complex outside Sao Paulo, officials said Monday.

Authorities were investigating a possible connection between the first two uprisings in the jungle states of Rondonia and Roraima, police said. Ten prisoners died in the mutiny in Roraima, while eight others were killed in a similar riot about 800 miles (1,300 kilometers) away in the penitentiary in Rondonia.

Roraima’s justice secretary Uziel Castro said at least seven of the bodies were piled up and burned after the Sunday prison mutiny in that state. At least two other bodies were found in a different section of the Monte Cristo prison, but it wasn’t immediately clear where the tenth was found. Castro says at least three of the bodies were beheaded and efforts to identify them have been slow.

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