The fire marshal said there was a party at the third-floor apartment and people were jumping up and down, causing the floor to collapse.
Glenn says at least 30 people were in the apartment when the floor gave way, although some witnesses and Twitter video of the incident show more people. Some people drove themselves to the hospital.
Denton firefighters believe the cause of the collapse was too much jumping.
Many who were at the party could be seen crawling over beams and plywood after the collapse.
It hasn't been confirmed whether "structural issues" at The Ridge Apartments on Colorado Boulevard are to blame.
Denton police said there was a large party happening in a 3rd floor apartment during the collapse.
Carroll says she and her roommates have complained about the loud and large parties over the past three months."This happens nearly every weekend", she said.
"I grabbed my keys, my wallet and I left to the police department", she said. I told my roommate, 'We're leaving.
Carley Carroll is a UNT sophomore who lives on the second floor directly below the unit that collapsed.
The apartment is at the Ridge at North Texas, a complex that houses students from three schools: University of North Texas, Texas Women's University and North Central Texas College.
Denton Police told FOX 4 they have received previous noise complaints, but people have mostly left the party by the time officers arrive.