Police are investigating a spate of threats in multiple school districts amid a threat uptick that is sparking concern among parents.

Police say there have been 42 threats so far in Nassau in 2018, with three just yesterday.

Nassau County police were at Valley Stream South High School Monday after they say someone made a threat on social media claiming there would be a shooting at a Valley Stream school at 12:27. It prompted a panic among parents in the district, some of whom signed their children out of school before noon.

At Farmingdale High School on Friday, police say a 17-year-old was arrested for allegedly threatening that he was going to shoot up the school. Police say the teen, 17-year old Youssef Mohammed, was charged with making a terroristic threat, a felony.

North Shore School District schools were briefly put on lockout mode Monday while police investigated a possible threat, but after-school activities were being held as scheduled.

And a message on the Southampton School District website Monday said that three buildings were being put in lockout mode due to an unspecified threat about Suffolk schools. All after-school activities were canceled.

Suffolk police say they are also investigating a message posted in an online chat room regarding a threat of violence in the Sayville School District. They're urging anyone with information in that case to call them at 631-854-8526 or to call Crime Stoppers at 1-800-220-TIPS.

And Lawrence High School Superintendent Dr. Ann Pedersen said Monday that police investigated after students reported a classmate who had posted an inappropriate comment on Snapchat over the weekend. No arrest was made in that case and officials say there was no credible threat, but the school is urging parents to monitor their children’s social media use.

Nassau Police Commissioner Patrick Ryder says false threats will not be tolerated, and those who make them will be charged with making a terroristic threat, a class D felony punishable by up to seven years in prison.