A video posted online captured the moment when dozens of students suddenly plunged into a lake in Madison, Wisconsin, after a pier holding them collapsed Monday afternoon.

About 60 to 80 people were standing on the swimming pier in front of the University of Wisconsin-Madison when it fell apart, according to the Madison Fire Department. Officials said six people were hurt and treated by EMTs and paramedics, and one of them was taken to a local hospital with non-life-threatening injuries. 

Five students were hurt and another was hospitalized after a pier in Madison, Wisconsin, collapsed during Labor Day celebrations on Monday. pic.twitter.com/3smfjI6PUV

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The University of Wisconsin-Madison said in a statement that a "number of students and other members of the public were on the pier" at the time. 

Many swam back to shore after the collapse. The school said the swimming area was not staffed by lifeguards.

"The pier is currently closed, and UW–Madison will investigate what occurred. The pier was due to be removed on Tuesday for the end of the summer season," the school said in a statement. 

Christopher Brito

Christopher Brito is a social media manager and trending content writer for CBS News.