As many as 50 people were inside the OAW Sports Complex in New Berlin Tuesday night when part of its roof gave way.
No injuries were reported.
Heavy rain was falling shortly after 7:45 p.m. when the New Berlin Fire Department received the emergency call.
New Berlin Mayor Dave Ament says rainwater got trapped on the roof and may have caused the collapse.
For now, no one is allowed to go inside the building because it is “very unsafe.”
City inspectors are working with structural engineers to determine why it collapsed.