Seven workers were killed in an industrial accent at the Grupo Modela brewery in Mexico City, the company that makes Corona Beer.

Grupo Modelo released a statement saying it “is deeply sorry for this incident and will support the affected families permanently.”

The company says it is cooperating with authorities investigating the accident, which happened in a tank that was undergoing maintenance and cleaning, but no other details were provided.  Mexico City prosecutors says investigators are looking into whether the workers died from inhaling toxic fumes while cleaning the inside of the cistern.

Belgium-based Anheuser Busch InBev is in the process of taking control of the the family-owned Grupo Modelo, the sixth-largest brewer in the world.