BENTON — Thirteen students riding in a school bus on Interstate 95 late Thursday were taken to Waterville hospitals after they reported feeling ill, apparently from fumes caused by an overheated bus engine.

Fairfield-Benton Fire & Rescue Chief Travis Leary said Friday his department got a call at 10:21 p.m. about a bus parked on the southbound side of Interstate 95 in which students had possibly been exposed to antifreeze. He and his crew and about a dozen area ambulances headed to the scene, near the Kennebec River Bridge, he said.

“We ended up transporting 13 total, for various ailments — headaches, some nausea, stuff like that,” Leary said.

The students, from Edward Little High School in Auburn, were taken to Thayer Center for Health and Northern Light Inland Hospital, both in Waterville.

Auburn School Department Superintendent Susan Dorris said Friday afternoon in an email that the students had been at a track meet at Nokomis High School in Newport and were heading back to Auburn when the incident occurred.

“The students who were transported to area hospitals were evaluated and have since been released,” Dorris said. “We’re pleased to report that all students are recovering and are expected to be fine. There were no serious health impacts reported.”

She said the bus engine overheated, which released fumes inside the bus, although officials don’t know what the fumes were or what specifically caused the students to feel unwell.

“The incident is under investigation by the district and transportation staff and the exact mechanical cause is still under review,” Dorris said.

She said officials are not aware if the bus driver reported feeling ill.

Because of the number of patients needing help, it was considered a mass casualty incident, said Leary, the fire chief.

Leary said tests for carbon monoxide were negative. There had been a small antifreeze leak from the bus, he said.

Everyone got out of the bus and waited on scene for another bus from Auburn to arrive to pick them and their belongings up, and by that time, it was just before midnight, Leary said.

About six firefighters from Fairfield-Benton responded. Also responding were Delta Ambulance, three Waterville Fire Department ambulances, two ambulances each from Winslow, Clinton and Sebasticook Valley Hospital, and one from Redington-Fairview General Hospital in Skowhegan, Leary said. He said two emergency medical personnel were on each ambulance. The Sebasticook Valley ambulance had been stationed at Inland, he said.

Dorris, the Auburn school superintendent, said Maine State Police also responded to the scene, where rescue workers had promptly responded.

“The school district is conducting a full review of the incident in accordance with its post-incident protocols,” she said. “School officials would like to acknowledge and thank the Waterville area first responders for their swift and professional response. Their actions, along with those of our coaches, transportation staff, and high school administrators, ensured the safety and well-being of our students during a challenging situation.”