The malfunction occurred at about 3 p.m. Thursday, causing minor injuries to five children and two adults.
Mitchell said a connector link on a chain appears to have pulled apart, causing the chain to dangle in front of the ride and hit the passengers.
Mitchell said the ride was shut down for inspection after the incident, and the California Division of Occupational Safety and Health cleared the ride for repair Thursday evening.
An independent ride inspector called Coulter & Associates is also reviewing the incident, Mitchell said.
Although a ride that injured a worker at the Sonoma-Marin Fair in Petaluma last week was also called the Wacky Worm, Mitchell said the ride that malfunctioned Thursday is not the same one.
The Alameda County Fair's ride is owned and operated by Butler Amusements, Mitchell said. The Sonoma-Marin Fair uses Brass Ring Amusements' Midway of Fun.
On June 23, a worker's leg was severed below the knee at the Sonoma-Marin Fair when he tried to cross the Wacky Worm's tracks while the ride was in motion, fair officials said.