Brazilian mining firm Vale activated alarms in areas below three tailings dams on Wednesday night due to an elevated risk of rupture, amid a tense atmosphere in Minas Gerais state where a dam burst in January killed about 300 people.
The company activated alarms in areas downstream of the B3/B4 dam and the Forquilha I and Forquilha III dams as a "preventative measure," after the structures failed to receive a safety certification from independent auditors.