Capt. Dexter Nelson said there have been no arrests in the 11:30 p.m. Monday fight in the Bricktown entertainment district.
"All we're hearing from some of the witnesses is there was pushing and shoving in the area," Nelson said. "Apparently a group of girls got into it with some guys. It was shortly thereafter that gunfire erupted."
Emergency Medical Services Authority spokeswoman Lara O'Leary said seven people were taken to a hospital with gunshot wounds and that a pregnant woman was also taken to the hospital after she was assaulted in the scuffle.
O'Leary said the woman and six of the gunshot victims were in good condition Tuesday morning. One person was in critical condition.
Nelson said it wasn't clear what sparked the gunfire or if anyone involved had attended the Chesapeake Energy Arena to see the Oklahoma City Thunder eliminate the Los Angeles Lakers to advance in the playoffs.
"It doesn't appear that what happened had anything to do with the game," he added.
Nelson said police are struggling to track down witnesses but are checking with nearby businesses that may have surveillance cameras that captured the incident.
A spokesman for the Thunder did not immediately return a phone call seeking comment on Tuesday.