(NEWSnet/AP) — A carbon monoxide leak at a Pennsylvania day care center sent nearly 30 children and four adults to the hospital early Tuesday.

Officials say none of the injuries are considered serious.

Emergency responders went to the Happy Smiles Learning Center in Allentown, Pennsylvania, on reports of an unconscious child.

Authorities say the building was evacuated after air quality detectors worn by firefighters were triggered.

The leak was caused by a malfunctioning heating unit and a blocked venting system, investigators said. They noted the building did not have carbon monoxide detectors, which will be required for child care facilities under a new state law that has not fully taken effect yet.

Copyright 2022 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed without permission.