Police officers were on the scene of a "critical incident" at Milwaukee's Molson Coors headquarters, which local news media described as a shooting with multiple casualties.
'Critical incident' reported at Molson Coors facility in Milwaukee
The Milwaukee Journal Sentinel, citing unnamed sources, said multiple people had been killed.
That report could not be immediately confirmed.
A message posted by the Milwaukee Police Department on Twitter said only that police were "investigating a critical incident" and urged the public to "stay clear of the area" near the city center.
No further official information was immediately made available.
A Molson Coors security official said: "We have no information at this time."