(RNS) At least 16 Jewish community centers received bomb threats on Monday (Jan. 9) in an apparent attempt to rattle American Jews, who have seen a spike in anti-Semitism incidents in the past year.

The threats — some by live callers, some by robocall — were made to JCCs in Florida, Maryland, New Jersey, Tennessee, South Carolina and at least four other states.

All of the reports were false, but several forced the evacuation of centers, which are gathering places for Jews and often include preschools, senior centers, gyms and facilities for readings, classes and prayer.

The Jewish Chronicle of London also reported bomb threats at “small number” of Jewish and non-Jewish schools in Britain on Monday. These were also determined to be false.

Targeted JCCs included those in Baltimore; Miami; Columbia, S.C.; West Nashville, Tenn.; and Jacksonville, Fla.

Law enforcement officials are investigating the possibility that the calls came from a single source.

The Jewish Community Center Association of North America — the umbrella group of JCCs — thanked local and federal law enforcement authorities Monday afternoon for their “quick and thorough response.”

The backdrop to the threats is a rise in anti-Semitic incidents in the U.S. during the past year, which experts have connected to anti-Semitic supporters of President-elect Donald Trump who have been emboldened with his rise to power.

Trump has refused to heed many Jewish leaders who have asked him to sever ties with aides and other supporters who they accuse of trafficking in anti-Semitic language and symbols.

“We were grateful that this time no one was hurt but, sadly, we know we can’t let our guard down,” said Michael Siegal, former board chair of the Jewish Federations of North America.

David Posner, director of strategic performance at the JCC Association, said JCCs will continue to work with law enforcement “as they do all year long” to ensure the safety of the centers.

“We are proud of our JCCs and grateful for their professional staff, who in the face of threatened violence today, responded quickly, calmly and professionally by implementing well-practiced evacuation procedures and ensuring that no one was harmed,” Posner said.

The Jewish Telegraphic Agency reported that on Wednesday (Jan. 11) the FBI and Department of Homeland Security will conduct a conference call with Jewish community leaders Wednesday to discuss the incidents and protocols for handling such threats in the in the future.