Two employees from Alamos Gold’s Mulatos mine in Mexico’s Sonora state are “missing and presumed dead” after an accident at the mine, the company reported on Thursday night.

Alamos said an “unexpected pit slope movement” occurred in the open pit mine’s El Salto area, where the company has been conducting pre-stripping activities.

The company said a search and rescue team is working to reach the location where the two workers were last seen. It has launched its own investigation and contacted authorities, and reached out to the workers’ families to provide “all means of support.”

Alamos president and CEO John McCluskey said in a statement that the company was “profoundly saddened” by the accident. “The safety of our employees is our highest priority and the loss of these two individuals is a shock to us all,” he said.