ANGELS CAMP -- Three people attending the annual fair celebrating the popular Calaveras County jumping frog contest were seriously injured Friday during the collapse of a carnival ride.

Another 14 riders also were hurt, but their injuries were considered minor, said Dennis Townsend, a chief in the Calaveras County unit of the California Department of Forestry and Fire Prevention.

The three most seriously injured riders were being airlifted to area hospitals, he said.

Townsend said they were injured when a type of swing ride collapsed shortly after 6 p.m. Friday. The ride has arms that fling out as they spin around an axis.

He said he did not know what might have caused the collapse or specifically how the riders were hurt. KCRA-TV in Sacramento reported that 25 people were on the ride when it collapsed.

State accident investigators were en route to the fairgrounds.

Laurie Giannini, the fairground's marketing director, said the fair remained open Friday night but the carnival area was shut down following the accident. She said there were no fatalities and that the riders who received minor injuries had been treated.

The Calaveras County Fair and Jumping Frog Jubilee is held each year in late May and was inspired by the Mark Twain story, "The Celebrated Jumping Frog of Calaveras County."

Twain's tale focuses on a character and his jumping frog, named Dan'l Webster. The fictional frog-jumping contest is rigged in one gambler's favor when he secretly fills his opponent's frog with buckshot.

The Calaveras County fairgrounds is located just outside the Gold Rush-era town of Angels Camp in the Sierra Nevada foothills, about 80 miles southeast of Sacramento. It bills itself as an "old-fashion county fair" with exhibits and a variety of entertainment.

Last year's jumping frog contest drew 4,000 entries. This year's final is scheduled for Sunday.

The jubilee has been held since 1928, according to the Union Democrat newspaper of Sonora.