A fight broke out at about 10:10 p.m. after gang signs were flashed, resulting in three people being stabbed, police said.
A 14-year-old boy was stabbed in the arm and rib while a 15-year-old boy was stabbed in the armpit, police said. Both were transported to the hospital in stable condition.
A 30-year-old man who was not involved in the fight was stabbed in the face and arm, but could not remember details of the stabbing and did not see the suspect, police said. He was transported to the hospital in stable condition.
At the venue, someone threw what police believe to be firecrackers, which caused a crowd of people to run out of Navy Pier. Chicago police spokesman Anthony Guglielmi said someone in the crowd yelled that there was a gun.
Fourteen others were injured in the stampede near Harry Caray's Tavern, police and fire officials said. Officials said none of the injuries appeared to be life-threatening.
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A 16-year-old boy punctured his leg after running into a table and was transported to Northwestern Memorial Hospital in stable condition. Authorities initially believed that he had been stabbed.
Witnesses described a chaotic scene, with parents separated from children, fences collapsing, elderly people falling down.
"We were on the Sea Dog and our trip was about to be over and then all of a sudden we just heard the loudest screams and I turned and I saw everybody drop to the ground," said witness Lucila Pulido. "It was the scariest thing ever. Then we saw people running with strollers, there's shoes everywhere, people just ran for their lives. It's so sad because this is a such beautiful city."
Police said that everyone entering the "secure area" on the pier was screened for weapons, but the stabbings happened outside of the "secure area."
Police said they are currently searching for two suspects in connection with the stabbing.