Chicago, IL- More than 100 students and several staff members were hospitalized Thursday after high carbon monoxide levels were reported at a Chicago elementary school.

Fire officials said CO detectors alerted Horace Mann school officials to the high reading Thursday morning as school was starting. Students were quickly moved to another building.

The fire department said the students and staff were all transported to the hospital as a precaution.

The cause of the high carbon monoxide levels was not immediately known.

All Chicago Public Schools received new carbon monoxide detectors in classrooms after a malfunctioning boiler released carbon monoxide fumes into an elementary school on the city’s Northwest Side in late October.

“CPS appreciates the Fire Department’s precaution and quick action at Mann this morning, as the safety of our students and staff is of the utmost importance to the district,”CPS said in a statement. “We are in contact with parents of affected students, and we will work with the Fire Department to get to the bottom of what happened today. Over the course of the last month, CPS has installed more than 5,900 carbon monoxide detectors throughout the district.”