SÃO PAULO, Brazil — The Brazilian police on Friday arrested eight employees of the giant mining company Vale on suspicion of first-degree murder as part of a criminal investigation into a dam rupture that killed over 160 people.

The dam, filled with mining waste and sludge, burst three weeks ago, sending a tidal wave of mud crashing down on the company cafeteria at a mining complex in Brumadinho in southeastern Brazil. The torrent continued downhill, slamming into homes and contaminating rivers. At least 166 people were killed and 147 remain missing.

The eight people arrested were “fully aware of the instable situation of the dam,” the judge, Rodrigo Heleno Chaves, said in the arrest warrant, citing evidence collected over the last three weeks.

He said a “drastic variation” that was recorded in monitoring instruments just days before the collapse, along with anomalies registered since mid-2018, should have prompted an immediate evacuation.