(CNN)-- One person was killed and six people were hurt Saturday afternoon after shots were fired and a stabbing occurred at a motorcycle show in Denver, police said.
The violence broke out at about 12:45 p.m. (2:45 p.m. ET) during Colorado Motorcycle Expo weekend at the National Western Complex, said Denver police spokeswoman Raquel Lopez.
Three people were listed in critical condition at Denver Health Medical Center and three were in stable condition, said Dr. Kevin McVaney, an emergency physician. He would not specify what kind of injuries they suffered.
Denver Health earlier tweeted that nine people had been taken to area hospitals.
Lopez did not say whether the person killed was stabbed or shot. Nobody had been arrested, she said, though men led away from the event in handcuffs were being questioned.
As a safety precaution, the hospital emergency department was locked down until about 4:30 p.m. (6:30 p.m. ET), according to a medical center tweet.
The Denver Post quoted a witness as saying the feud was started by rival biker gangs. The witness asked to remain anonymous because of fear of retaliation, the newspaper said.
Bob Cook, who was running a booth for leather goods at the expo, told the Post he heard shots and saw people dive under tables. He didn't know what caused the shooting but said that minutes later the scene returned to normal despite puddles of blood on the floor.
Britney Shaw, who was working at a jewelry stand, told the Post she saw a group of about 50 men brawling on the stairs, which were covered in blood and cordoned off.
Lopez was asked whether motorcycle gangs were involved. She said she didn't know. Video showed men wearing vests with patches gathered outside the hospital.
The complex is near the Denver Coliseum. Police initially tweeted that the incident occurred at the coliseum.
Organizers of the motorcycle expo have not announced whether the event will be held on Sunday.
CNN's Carma Hassan contributed to this report.
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