Students at Fitzgerald Elementary School in Waltham were forced to evacuate the building on Tuesday after a bomb threat was called in to school administrators. The threat was one of over a dozen sent to local public schools in the Boston area, according to boston.com. The Federal Bureau of Investigation has begun a formal investigation into the threats.

Waltham, Newton and Boston were among the cities targeted, in addition to Groton, Weymouth, Taunton, Arlington, Plymouth, Salisbury, Ayer, Tewksbury, Billerica, Swampscott, Kingston and Westford. Many of the threats were called in via phone, and some were made using an automated calling system, according to CBSBoston. State Police officials have not released the content of these messages as of press time.

Though no bombs were found at any of the threatened schools, the FBI is still working closely with state and local officials, including the Commonwealth Fusion Center, which focuses primarily on homeland security and emergency response.

“Even when they are low level incidents like this where we’re getting robocalls or continually seeing computerized threats, you can’t just dismiss them. You need to do something reasonable,” Director of the Massachusetts Association of School Superintendents Tom Scott said regarding the incidences, according to CBSBoston.

After the initial round of threats on Tuesday, additional threats were made against schools in Falmouth, Bourne, Mashpee, Plymouth, Weymouth, Arlington and Boston on Friday, though it is unclear whether these sets of threats were related. According to Massachusetts law, the penalty for anyone convicted of making bomb threats includes possible prison time up to 20 years, a fine of up to $50,000 or both. Additionally, those convicted of making bomb threats may also be held responsible for paying restitution for state and local resources used in investigating the threats.

—Abby Patkin