One adult was also among the 13 people transported to hospitals after the mishap at Norwalk's Oyster Festival.
Norwalk police Lt. Paul Resnick said an 8-year-old boy was admitted to a hospital with non-life threatening injuries. The rest were treated and released.
Five other people refused treatment at the scene, police said.
The rotating, swing-type "Zumur" ride lifts riders up and away as it spins, authorities said. State police said a mechanical failure caused the ride to suddenly stop and those on board collided with each other.
Police initially said some of the ride's occupants had fallen to the ground but a preliminary investigation by state police indicates no riders were ejected from the ride or fell from it.
Resnick said children were being tended to by their parents on the ground when he arrived shortly after the accident.
The festival's organizer, the nonprofit Norwalk Seaport Association, said it directed the ride's operator, Stewart Amusement, to shut down the entire ride area until state inspectors completed a check. The other rides later reopened and the rest of the festival remained open on its third and final day.
Stewart Amusement didn't immediately return phone and email messages seeking comment. Its rides are inspected by its own staff every day, by state and local inspectors weekly and by engineers and insurance inspectors each year, the company's website said.
"Your safety is of critical importance to us," the site says. "Not only do we have an obligation to provide our guests with the safest equipment and environment possible, but also our ultimate success depends on it."
Stewart Amusement says it has provided rides and other attractions since 1983 at events in Fairfield and New Haven counties in Connecticut and neighboring Westchester and Putnam counties in New York.
Troopers with state police fire and explosion unit were investigating, department spokesman Lt. J. Paul Vance said.
Festival organizers posted a statement about the accident on its Facebook page.
"Our first and only concern is for the wellbeing of those involved and their families," the statement said.