Story highlights Shooting happened about 1 a.m. Sunday at The Spot nightclub in Miami

Most of the victims were teenagers; some were only 11 years old, police said

Miami-Dade County has a midnight curfew on Saturday for people 16 and younger

No arrests had been made or suspects named by late Sunday

Fifteen people, many of them teenagers and some as young as 11, were shot early Sunday morning at a Miami nightclub, Miami-Dade police reported.

Police spokeswoman Frederica Burden said the victims ranged in age from 11 to 25 and were taken to area hospitals.

Several victims were released from hospitals Sunday afternoon and a person who'd earlier been listed as critical was upgraded to critical but stable, police said in a news release.

It's not clear whether the nightclub catered to teenagers. No public safety officials have explained why so many youths 16 and younger were inside a nightclub after the midnight Miami-Dade County curfew

Authorities said the shooting happened about 1 a.m. at The Spot nightclub at NW 64th Street and Seventh Avenue.

CNN affiliate WPLG said a large party was being held when shooting broke out. Witnesses told police they heard about 100 gunshots, WPLG reported.

"At this point, we are not sure if we have one shooter or multiple shooters," Burden said. No arrests had been made by late Sunday.

Police have yet to determine whether good surveillance video exists to help in the investigation, WPLG said. The club had recently begun to allow teen parties on the weekends, the affiliate reported.

Capt. Ignatius Carroll of Miami Fire Rescue said the scene was chaotic when emergency medical personnel arrived. Wounded people were found inside the club and on the sidewalk, he said.

"We understand there was a gathering taking place at some sort of little nightclub," he said. "We had a large crowd."

With so many wounded people, emergency responders had to treat some victims on the sidewalk.

Burden didn't know a motive for the shooting.

"Investigators are interviewing witnesses at this time, but we are also asking the public for their help by providing us with any information they may have on this incident," she said.