More than two dozen people were injured, including three critically, after a wagon overturned at an apple orchard in Wisconsin, authorities said.

The incident was reported Wednesday morning at Bushel and a Peck Apple Orchard in Chippewa Falls.

Elementary school-age children, parents and other chaperones were on a field trip at the time and were on a wagon ride, according to Chippewa County Sheriff Travis Hakes.

A tractor was pulling two wagons at a "low speed" on a public road when the accident occurred, Hakes said.

One of the wagons began to lose control and turn sideways as it descended a hill and overturned, resulting in injuries to both children and adults, Hakes said.

"It's a traumatic day for a lot of people," Hakes told reporters during a press briefing Wednesday afternoon.

Emergency personnel were dispatched for a "tractor accident involving two hay wagons with kids and adults," Chippewa Fire District Deputy Chief Cory Jeffers told reporters.

The fire department activated its mass casualty protocol so that outside agencies could help respond to the incident, Jeffers said. One helicopter from the Mayo Clinic was called in, he said.

Twenty-five individuals were transported from the scene to various agencies, Jeffers said. One patient was transported via the helicopter and nine via ambulance, Hakes said. Some were also transported in personal vehicles, he said.

Three people have life-threatening injuries and five have serious injuries, according to Hakes.

Marshfield Medical Center-Eau Claire received seven patients from the incident who are being treated for minor to serious injuries, a spokesperson confirmed to ABC News.

Hakes said he believes all patients are in stable condition.

Authorities did not release additional details on the victims, including how many were children.

Hakes called the incident "heart-wrenching."

"As a parent myself, it's a parent's greatest fear that something happens to their children," he said.

He said he responded to the scene and helped calm the children and reunite them with their parents.

"The children were extremely brave, very resilient," he added.

The scene has since been cleared, Jeffers said. All of the children who were still at the scene have been reunited with their families, he added.

The children attended St. Mark Lutheran School in Eau Claire, the school's principal confirmed.

"At this point, we are focusing on reuniting the children with their caregivers," Principal Peter Micheel said in a statement to ABC News. "Whenever we face a challenging time, we commit everything to the Lord's care and trust his guiding hand."

ABC News left a message with the orchard seeking comment.

Chippewa Falls is located about 12 miles northeast of Eau Claire.

ABC News' Alexandra Faul contributed to this report.