The Bergen County Sheriff's Office Bomb Squad was en route to sweep the building, Metzler said.
Students at Fair Lawn High School were moved to Memorial Middle School due to the threat.
It's the second time in as many weeks that multiple schools in MA and DE have simultaneously received threats. At least three of the schools received them over voicemail, authorities said. The preschool has already been searched by a bomb-sniffing dog, which is going school to school in Garfield. Students returned to Bergenfield High School in late morning after it was declared to be safe. The recorded message said a bomb would be placed in one of district schools and also threatened a "mass shooting" that would take place Tuesday. Parents were seen lining up at Teaneck High School to pick up their children after the threats.
Bomb or shooting threats led to evacuations or lockdowns for at least nine New Jersey schools on Tuesday, NBC New York reported.
Officers responded to Clifton High School, "where a coordinated effort between law enforcement and the school district was immediately initiated", police said.
The threats came to high schools in Leonia, Tenafly, Teaneck, Garfield, Fair Lawn, Hackensack, Englewood and Bergenfield, according to Bergen County Sheriff's spokesman Michael Saudino, as cited by the local media.