BERGEN COUNTY - Over 20 schools in 11 New Jersey towns were placed on lockdown or were evacuated Tuesday after threats were made against them.

According to law enforcement officials, the schools received the calls Monday night and Tuesday morning. The calls seemed to have been prerecorded and the caller spoke with a “robotic” voice. 

The threats said there would be bombs in the schools. Some of the calls also threatened a mass shooting of law enforcement officers who responded to the schools, according to police.

The threats were leveled against schools in Garfield, Bergenfield, Leonia, Fair Lawn, Englewood, Hackensack, Tenafly, Clifton and Sayreville.

Local police departments and the Bergen County Sheriff’s Department came to the schools to investigate. Bomb-sniffing dogs were brought in to look for any type of explosive device. Officials were able to determine that there were no threats at any of the schools.

Bergen County Sheriff Michael Saudino saidthat all the calls seemed to come from the same place.

“Apparently this is coming through recycled, computer-generated numbers, all from Bakersfield, California,” he said.

The sheriff added, “It's my hope that federal legislation will look at this thing and stop the protection of some of the companies where they hide the identity of people doing these types of calls."

The Bergen County Prosecutor’s Office and the FBI are assisting in the investigation.

So far, no arrests have been made. No one was hurt during the incident.

Schools in Massachusetts and Delaware also received calls, but it is not known if the incidents are related.