The Chicago Police Bomb and Arson unit and officials from the Bureau of Alcohol Tobacco Firearms and Explosives said a "pyrotechnic type of firework" prompted an hours-long investigation at an elementary school on Chicago's South Side Wednesday.

Just before 10 a.m., school officials discovered a hole in the roof of the Columbia Explorers Elementary Academy at 4520 S. Kedzie.

Children were moved from the school to an adjacent building as a precaution, according to police.

Authorities believed the incident happened Tuesday night and damage was discovered Wednesday morning.

Officials initially said the damage may have been caused by fireworks, but Tom Ahern with the ATF later said both the ATF and CPD Bomb and Arson Unit were at the scene investigating a possible explosive device on the school's roof.

ATF and @Chicago_Police Bomb & Arson Unit on scene investigating explosive device on rooftop of Columbia Academy school. 4520 S. Kedzie. — Tom Ahern (@TomAhernCPD) September 21, 2016

Just before 4 p.m., authorities determined the device was a "pyrotechnic type of firework."