An airline spokesperson said 13 people were treated at a local hospital.

WFXT spoke with a passenger who said she was sitting next to a teenage girl who started to feel sick mid-flight. She then realized more than a dozen other passengers surrounding her were violently ill.

"It was gross, because you have people vomiting and one of them was next to me, it was gross,” said the woman, who asked not to be identified. “I smelled that thing!"

The witness said she felt fine during the flight, despite what was happening around her. She told WFXT she believes the passengers were feeling sick before boarding.

"It’s something they had before,” the woman said. “One of them was following me getting on the plane and we were waiting (in) the line ... I saw that girl, she kept saying, ‘I feel sick. I feel sick.”

All of the sick passengers from the student group were sent to the hospital directly from the tarmac.

"They got us out first -- everybody out first," the woman said. "The ones that were sick, they stayed on the plane and talked to the medical team."

She said she was worried her children would become ill, but she said everyone she was traveling with was feeling OK after the flight.

American Airlines says no one else outside the student group reported feeling sick. Massachusetts Port Authority Spokeswoman Samantha Decker and Boston EMS officials said the passengers' symptoms were considered minor.

Decker said she didn't have information on what may have caused the illnesses.

The Associated Press contributed to this story.