Brazil’s mining regulator ordered 56 tailings dams to close April 2, citing physical instability or lack of documentation attesting to their stability.

The nationwide tailings dam shutdown occurred after Brazil’s National Mining Agency, known as ANM, raised minimum waste-dam security levels in the weeks following the Jan. 25 collapse of an iron-ore tailings dam, owned by Vale SA, in Minas Gerais state.

The collapse caused a mudslide that killed more than 200 people and polluted several hundred kilometers of the Paraopeba River.

The order to close takes effect immediately. Companies that fail to comply face the maximum ANM...