The incident took place at about 7 p.m. July 5. There were no injuries, but the kids had to wait about 20 minutes for a ladder truck from the Livermore-Pleasanton Fire Department to bring them down.
"It's a 'Zillerator,' a roller coaster -- it just stopped at a break, where it starts to come up on the rise," said Angel Moore, the Fair's interim marketing director. "It just basically got stopped on the track."
She said the Alameda County Fire Department keeps some staff on site during the Fair. They needed more equipment, so they sent out a call to the LPFD.
"They called us on mutual aid," said LPFD Batallion Chief Joe Testa. "We responded with an engine and a truck company."
Mutual aid is a cooperative agreement between emergency workers including firefighters and police officers.
"What they really needed for this was aerial apparatus," Testa said. "We laddered the roller coaster and brought four people down. Our crews secured the roller coaster so it couldn't move."
He estimated the height of the rescue at about 45 feet.
Seven LPFD firefighters responded to the call and helped the four young people down in what Testa called "a fairly routine truck operation."
The kids were strapped into safety harnesses and off the coaster about an hour after firefighters arrived.
It's relatively unusual for rides at the Fair to break down, Moore said.
"Rides get stuck all the time at all different places, but we don't have that happen a lot here," she said.
The last time a ride at the Fair broke down was in July 2010, when the "Wacky Worm," also a roller coaster, malfunctioned and caused minor injuries to five children and two adults.
A connector link on a chain in that ride pulled apart, causing the chain to dangle in front of the ride and hit passengers.
That same year, about 70 people were injured when they were swarmed by yellow jackets during a fireworks display, but a search of recent history showed no other ride malfunctions at the Fair.