MADISON, Wis. (AP) — A pier filled with people celebrating Labor Day on the University of Wisconsin-Madison campus partially collapsed into a lake, leaving one person hospitalized and slightly injuring about 20 others, officials said.

Video shot from Lake Mendota’s shoreline shows that a part of the metal pier just east of the Union Terrace’s campus stage collapsed Monday afternoon, sending some people falling into the water.

The Madison Fire Department said one person was taken to a hospital with non-life-threatening injuries and five others were treated at the scene for minor injuries. UW-Madison Police Officer Jeff Kirchman told the Wisconsin State Journal that “20 or so” had minor injuries, in addition to the person who was hospitalized.

“There were way too many kids on the piers. They were packed. There was no warning. All of a sudden it went down and people were in the water,” said Debra Drewek, a retired nurse who was taking pictures at the terrace when the collapse occurred.

She said many of the people on the collapsed section swam to shore and that others clung to the pier and waited for rescue boats to arrive. Drewek said most of the injuries appeared to be leg scrapes, and that “a lot of kids were crying because they had laptops, wallets and phones underwater.”

Kirchman said efforts were being made to recover lost items from the lake.

UW-Madison officials said in a statement that the swimming area was not staffed by lifeguards at the time of the collapse and that the pier was scheduled to be removed Tuesday due to the end of the summer season.