Linebackers Martez Smith and Tim Green and defensive end Deddrick Jones were shot just after 1:30 a.m., Hattiesburg police spokesman Sgt. Allen Murray said.
No arrests have been made, and police did not comment on possible suspects. Murray said it's possible the shooting was gang-related.
Murray had previously said the fight happened at Remington's Hunt Club. He said the fight started inside the club, then spilled out into the parking lot, where the players were shot.
Club officials told The Hattiesburg American in October that they typically have 20 security staffers on duty on weekends, when crowds can swell to as many as 1,000.
The club's website www.huntorbehunted.com shows numerous photos of scantily clad women at the club, many of which appear to be from bikini and dance contests. The interior is sprawling, with dining tables, pool tables and a stage.
Smith, a 22-year-old, fifth-year senior, was the team's starting middle linebacker before a season-ending knee injury last month. Jones, a 23-year-old junior, has started all 10 games on the defensive line, making 26 tackles, including 3 1/2 for a loss. Green, a 21-year-old junior, has played in seven games as a backup, making four tackles.
The incident happened just hours after Southern Miss beat No. 25 Central Florida 31-21 in Orlando. Jones and Green played in the game.
"During this difficult time our thoughts and prayers are with these three members of our Southern Miss family, Martez, Tim and Deddrick, as well as their families," USM coach Larry Fedora said in a statement released by the school. "These three men are an integral part of the success of our football program, and we will continue to keep them in our hearts and hope for a speedy recovery."