State officials were investigating Saturday whether mechanical or human error caused the first major ride accident at Disney's California Adventure, in which at least 15 park visitors suffered minor injuries the day before.

The California Screamin' roller coaster will remain closed for several days while investigators look at the ride's dispatch coordination to determine whether a computer failed or a person caused the accident, said Len Welsh, acting chief of the California Division of Occupational Safety and Health.

"The timing was part of [the accident]," he said. "We won't reopen the ride until we understand what caused it, to make sure it is safe."

Welsh could not say how long the investigation would take.