CHICAGO (CBS) — A total of 13 students from James Otis Elementary School,  525 N. Armour St., became sick during art class and were transported to the hospital on Thursday, according to the Chicago Fire Department.

The fourth- and fifth-grade students were painting when they started feeling sick, complaining of nausea and headaches.

“We were in our art class and we were painting and me and my friend felt like throwing up,” 10-year-old Mathew Moro said from the hospital waiting room. “I asked the teacher if I could go to the bathroom and I was crying.

“It was, like, really bad and I threw up in the bathroom.”

Other students were crying, too, he said. It was a frightening moment during what is normally one of the students’ favorite classes.

Sedell Johnson’s 10-year-old niece, London, was among those overcome by fumes.

“She’s doing well,” Johnson said. “She has a headache, so we are anxious to see what’s going on with that.”

Officials with Chicago Public Schools say the hospital transports were conducted out of an abundance of caution and that the situation is under investigation.  Officials have not said what type of paint was being used.

Four students were sent to Presence St. Mary Hospital, three were sent to UIC Medical Center, three were sent to Rush University Medical Center and three were sent to Stroger Hospital.

All of the students were in good condition, according to the fire department.

The school sent home a note to parents at the end of the school day:

Dear Parents and Guardians,

The safety of your children is always our top priority, which is why we must inform you of an incident that occurred today at school. Several students in one of our classes became ill during an art class today. We contacted the Chicago Fire Department and CPS Office of Safety and Security, and out of an abundance of caution, several students were transported to the hospital. The families of students directly impacted by this incident were contacted directly, and the rest of the school day continued without interruption.

This situation is under investigation and we will update you as soon as possible with more information. Please contact the school directly with any questions or concerns.