YONKERS (CBSNewYork) – Mold has forced hundreds of students from their school in Yonkers.

Paideia 15 was shut down Monday after officials found one fourth of the ceiling tiles in sections of the school tested positive for mold.

Cleanup is now underway, but officials do not know when students and staff will be allowed back inside.

Grades k through four were relocated to Robert C. Dodson School, while grades five through eight were sent to Roosevelt High School.

CBS2 recently spoke with a mold expert who said this summer’s excessive rainfall lead to a moisture build-up that encourages mold growth. He said not all mold is dangerous, but the only way to tell is to send samples to a lab.

“It tells us whatever is floating through the air, it tells us how much of it it is, and then it tells us what possible effects it can have on people,” said Michael Mercadante.

Paideia 15 isn’t the only school affected by mold this season. Two New Jersey schools had to push their first days back to clean up mold. Over the weekend, a mold scare at the New School in Greenwich Village also forced an evacuation.

Nearly 600 pre-K through eighth grade students attend Paideia 15.