Braintree High School is closed. No, not COVID — asbestos.

Students’ return to Braintree High School was delayed again Wednesday after it was revealed that the building needed asbestos testing.

District Superintendent Jim Lee told WCVB that tiles taken out by a subcontractor contained the potentially dangerous substance, which can be harmful if disturbed.

“A subcontractor doing some work in our building accidentally removed some tiles,” he said, according to the news station.

Parents were notified late Tuesday, according to WCVB. Officials hope to have the school reopened on Thursday. 

“We will provide additional information during the day tomorrow about the reopening of school and the schedule that will be followed,” the communication to the school community said, as shared by Boston 25.

“This information only became available at this late hour, and we understand the frustration and disappointment this message will elicit,” it read.

A broken pipe kept the school from reopening last week.