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At least 20 people have been killed in a stampede at a Chicago nightclub. Panic broke out when mace or pepper spray was sprayed into the air at the Epitome club in the city's South Side, reports say.
Many of the injured suffered breathing problems
The dead are believed to have been trampled as people rushed for the exits, according to emergency workers.
Dozens of other people were injured - some critically - in the stampede at about 0200 local time (0800 GMT).
Police officer Ozzie Rodriguez said: "There was some kind of congestion from within the establishment, people were heading for the door.
"Most of the fatalities appear to have been crushed or had injuries due to suffocation."
Reggie Clark, who was at the club with his sister, said: "Everybody smashed; people crying, couldn't breathe."
Attack fears
It is unclear what sparked the panic on the upper floor of the club on a busy Sunday night, ahead of the Presidents Day holiday on Monday.
One report said a fight broke out and pepper spray was used by club security officers to break it up.
Panic broke out on the upper floor of the club
A BBC correspondent in Washington says the high level of concern of a terrorist attack in the US - possibly using biological or chemical weapons - may have added to the panic when the substance was sprayed.
Clubbers rushed down a staircase to try to get out. When some fell, the crowd simply poured on top of them, witnesses said.
Fire chief Will Knight said there had been more than 1,500 people in the two-storey Epitome Night Club at the time of the disaster.
Medical teams from local hospitals were sent to the club with ambulances and paramedics to treat the casualties.
At least 20 people have been killed in a stampede at a Chicago nightclub. Panic broke out when mace or pepper spray was sprayed into the air at the Epitome club in the city's South Side, reports say.
Many of the injured suffered breathing problems
The dead are believed to have been trampled as people rushed for the exits, according to emergency workers.
Dozens of other people were injured - some critically - in the stampede at about 0200 local time (0800 GMT).
Police officer Ozzie Rodriguez said: "There was some kind of congestion from within the establishment, people were heading for the door.
"Most of the fatalities appear to have been crushed or had injuries due to suffocation."
Reggie Clark, who was at the club with his sister, said: "Everybody smashed; people crying, couldn't breathe."
Attack fears
It is unclear what sparked the panic on the upper floor of the club on a busy Sunday night, ahead of the Presidents Day holiday on Monday.
One report said a fight broke out and pepper spray was used by club security officers to break it up.
Panic broke out on the upper floor of the club
A BBC correspondent in Washington says the high level of concern of a terrorist attack in the US - possibly using biological or chemical weapons - may have added to the panic when the substance was sprayed.
Clubbers rushed down a staircase to try to get out. When some fell, the crowd simply poured on top of them, witnesses said.
Fire chief Will Knight said there had been more than 1,500 people in the two-storey Epitome Night Club at the time of the disaster.
Medical teams from local hospitals were sent to the club with ambulances and paramedics to treat the casualties.