TMZ reported 49 young women were hurt, with 14 taken by ambulance to a hospital for treatment.
Oslo police also nearly declared a state of emergency as tens of thousands of fans grew rowdy, the entertainment Web site said.
"I have already called on the Emergency Planning Agency to examine the entire event from the planning stage to its implementation," Oslo's Mayor Fabian Stang said after the incident. "We have to find out what went wrong and why it happened."
Swim Week Miami Beach 2014 [PHOTOS]