A bomb threat against a high school in Oregon over the weekend led officials to cancel Monday's classes and activities.

The threat against Summit High School in Bend, Oregon, was made Saturday on social media, and Bend-La Pine Schools sent a letter to families Sunday night to make them aware of the incident, KTVZ reported.

"After a meeting this evening with our law enforcement partners, we made the difficult decision to cancel all classes and activities at Summit High School on Monday, Sept. 11, in response to a threat that was posted on social media this weekend," the letter reads. It added: "Law enforcement agencies are actively investigating this threat, and we believe it is best for students to stay home tomorrow."

The district said it is working with the Bend Police Department in response to the since-deleted post that used "threatening language in reference to Summit High School, use of a destructive device, and tomorrow’s anniversary of the 9/11 attacks."

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All after-school activities, including sports practices and games, are canceled due to the bomb threat.

"With the assistance of Oregon State Police and the FBI, detectives are working to determine if the threat is credible or not," the letter said. "The school campus was searched today; an additional search will be conducted in the morning with the assistance of a trained OSP canine."

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Families were asked to contact the police department if they have information on who may be responsible for the threat. 

The district said it will provide families with an update by Monday evening.

Police have not yet identified a suspect.

Monday marks the 22nd anniversary of the deadliest terrorist attack on American soil when commercial planes were flown into the World Trade Centers in New York and the Pentagon on Sept. 11, 2001.