Two schools in the Middle Country School District briefly were under lockout Monday as Suffolk County police investigated bomb threats, according to district officials and police.

Both the Selden Middle School in Centereach and Newfield High School in Selden went into lockout mode after notifying police of the threats. One threat was made in a fax to the middle school, and that fax included another threat to the high school, according to a statement from the school district.

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Police said they were notified about the threats at 9:57 a.m.; they responded with their canine unit and “nothing was found,” a department spokeswoman said.

By about noon, both schools resumed normal operations, police said.

CORRECTION: The location of the schools and the name of the district were incorrectly identified in a previous version of this story.