NEW YORK (CBSNewYork) – Students were evacuated from Midwood High School Tuesday morning due to a bomb scare.

Over the past 24 hours anonymous calls have been made targeting schools, community centers, and even a subway.

Police have found no evidence of truth to the threats.

As CBS2’s Alice Gainer reported, police said someone called in an anonymous threat Monday, warning of a bomb set to explode on Tuesday.

Nearly 4,000 students are enrolled at Midwood High School in Brooklyn and all of them were evacuated from the building along Bedford Avenue after sources said multiple calls were made threatening the school.

The building was swept and students returned to class around 1 p.m.

In Manhattan, NYPD officers checked bags underground.

Law enforcement sources said someone called to say a bomb was going to explode on the 7 train between 34th Street and Main Street in Queens.

The NYPD was taking extra precautions — doing more inspections of stations and trains.

In Plainview Long Island police officers were stationed outside of the Middle Island Y-JCC. Pre-school students returned to class on Tuesday, after being evacuated on Monday after an anonymous bomb threat.

“An emotional experience more than anything else,” Robyn Kreiner said.

The JCC in New Rochelle was among six Jewish organizations targeted on Monday. Nearly 100 across the country have received similar threats since January.

“We were unfortunately waiting, it was only gonna be a matter of time,” said Mid Island Y-JCC, CEO, Rick Lewis.

Lewis said they routinely run bomb scare and lockdown drills and have security in place.

Nassau County police said they added resources during the Jewish high holy days,.

“The department has maintained and intensified patrols,” acting police commissioner Thomas Krumpter said.

Since 2017 began, the number of bomb threats clocked in at 136 compared to 83 at thsi time last year.

Police believe it’s copy cats who are coming in waves.

Former FBI agent Manny Gomez pointed out that it can be difficult to trace the caller, especially when it comes from overseas.

“Somebody can just simply buy what I like to call a throwaway cell phone from a Duane Reade, give a fake name, now you have a number that can’t be traced back,” he said. “They could be robots making the calls. There’s mention that it could be cloned phones.”

Police stressed that no viable devices have been found in any of the threats made.

There’s also no indication that the threats have been mad eon behalf of any organized group.