At least 14 Gresham Elementary students were taken to hospitals after a pepper spray discharge at the South Side school.
Officers responded about 11:30 a.m. to a report of release of possible pepper spray on the third floor the building in the 8500 block of South Green Street, Chicago police said.
The children were taken to Saint Bernard and Little Company of Mary hospitals, police said.
One child was being questioned, police said. Investigators believe the discharge may have been accidental, according to police.
A spokesperson for Chicago Public Schools did not immediately reply to a request for comment.
The incident follows a string of pepper spray discharges at Morgan Park High School over the last week. Wednesday afternoon, three students and two teachers were affected by an aerosol spray, police said. A day earlier, three other people were hit by spray at the same school. On April 25, two students were taken to the hospital after another student discharged pepper spray inside the school.
