A friend was stabbed in an arm.
Sgt. John Delaney says more than 250 people had gathered for the party at the Blue Fusion Bar and Grill. He says no security was on hand and many teens were drinking before entering the club, which has no liquor license or listed telephone number.
Police Commissioner William Fitchet says the attacker stabbed the unarmed teenagers "with little or no provocation."
Police are seeking a suspect. They say they hadn't made any arrests as of Sunday afternoon.