SHAW ISLAND - A hayride crash last weekend in the San Juan Islands that injured 40 - and left three people with serious injuries - involved churchgoers from three Whatcom County youth groups.

For about a week, the youths had been doing outdoor labor on a mission trip at Our Lady of the Rock, a Benedictine monastery of women on sparsely populated Shaw Island, said Greg Magnoni, communications director for the Archdiocese of Seattle.

The youth groups were from St. Joseph Parish in Ferndale, St. Anne Parish on the Lummi Reservation and an additional Bellingham parish, the name of which could not be confirmed as of late Wednesday.

On Sunday, July 24, the group, mostly made up of teenagers, went on a hayride to inspect the work they had done on the grounds.

During the steepest downhill part of the road, the trailer jackknifed with the tractor that was pulling it, spilling all of its passengers onto the compacted gravel road.

One person had to have a finger amputated. Another person had a serious ankle injury, and another had a badly hurt leg, Magnoni said. All three of the serious injuries involved people who were older volunteers. Several youths also were hospitalized.

The names of those involved were not released.

The crash remains under investigation. Deputies are looking into the heavy load of people and logs for seating that were piled on the trailer, along with maintenance of the tractor and trailer, said San Juan County Sheriff Rob Nou.

It's not clear whether the tractor driver, who was an adult parish volunteer, will be cited.

The Associated Press contributed to this article.