Conestoga High School in Chester County opened with a three-hour delay on Thursday after someone called in a bomb threat, the Tredyffrin/Easttown School District said.

Tredyffrin Township police were called to the school before 6 a.m. after the 911 Call Center received the threat and sent officers and a K-9 unit to the school. The K-9 unit was deployed to search the school building, police said in a Facebook post.

Before 9:30 a.m., police posted on Facebook that the school had been cleared and no threat was found.

"Authorities have determined the threat was a hoax, and the building has been cleared for students and staff to return. While the caller has not been identified, the matter remains under investigation," administrators said in a post on the school website.

The school district

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