A dam collapsed in an iron ore mine in Brazil’s Minas Gerais on Friday, killing at least seven people, AFP reported. Rescuers are searching for at least 150 people who are missing after a torrent of slush flooded Brumadinho and its vicinity, according to Reuters.

The dam is owned by Vale SA and the disaster has been described as the second major incident involving the company in three years. Around 100 rescuers are trying to save those trapped in the sludge and more are expected to join the operation.

Vale Chief Executive Officer Fabio Schvartsman said only one-third of the estimated 300 workers at the site had been accounted for. He added that a German company hired to assess the dam had shown it as stable.

Brazil’s President Jair Bolsonaro referred to the incident as a “serious tragedy” and deployed the ministers of environment, mines and energy, and regional development to the site.

In 2015, a dam break killed 19 people and caused major damage in Minas Gerais.