MEXICO CITY (AP) -- Mexico City authorities say seven workers died while cleaning a tank at a Grupo Modelo brewery in Mexico City.

A spokeswoman for city prosecutors says the accident occurred early Sunday and that investigators are looking into whether the workers died from inhaling toxic fumes. The official spoke on condition of anonymity because she was not authorized to discuss the case.

Plant manager Francisco Lopez Bravo told local media the workers were trapped inside the cistern while doing maintenance work.

Lopez Bravo said there are no other risks at the brewery and that it continued to operate on Sunday.

Anheuser-Busch InBev has been trying since June to take over the half it doesn't already own of Grupo Modelo, which makes Corona and other globally popular beers.