A nightclub owner, manager and party promoter were acquitted of involuntary manslaughter Friday in the 2003 stampede that killed 21 people at Chicago's E2 club.

Judge Dennis Porter agreed with defense attorneys that prosecutors had not proved their case, said Tandra Simonton, a Cook County state's attorney's spokeswoman.

The Feb. 17, 2003, stampede started after someone used pepper spray to break up a dance-floor fight, sending a mob of people fleeing down narrow stairs to an exit, authorities said. The force of the bodies piling against the doors prevented them from being opened. More than 50 people were injured.

Those acquitted are club owner Calvin Hollins Jr., club manager Calvin Hollins III and party promoter Marco Flores. Another club owner, Dwain Kyles, is being tried separately and was not affected by Friday's decision, Simonton said.

The acquittals came at the request of defense attorneys immediately after prosecutors rested their case and before the defense called any witnesses, Simonton said.

Prosecutors accused the defendants of not doing enough to protect patrons, including not enough exits and improperly marked exits.

They said videotape showed 1,152 people were in the club — roughly five times its capacity.

Defense attorneys said nobody could have predicted the tragedy, a mix of factors that led hundreds of patrons racing to the entrance, including a fight involving as many as 40 patrons and a disc jockey imploring security guards to use pepper spray on those who were fighting.

In addition, with the Sept. 11, 2001, terrorist attacks fresh in their minds, patrons added to the panic with yells of Osama bin Laden, anthrax and poison gas, defense attorneys said.