NEW YORK (JTA) — More than 50 Jewish community centers nationwide have received emailed bomb threats since Saturday.

None of the threats have been found to be credible, though local law enforcement agencies have been notified. Officials do not know who sent the threats.

JTA has learned from officials familiar with the threats that most of the JCCs affected received identical emails containing bomb threats. None of the emails, however, named the specific institutions in question or contained anti-Semitic language.

“Our goal has been — and we seem to be succeeding — to go about our day with as much normalcy as possible,” said Martina Hull, interim executive director of the the Sidney Albert Albany JCC in New York, which received a threat Sunday morning. “There was an indication of a threat and the Albany JCC was not mentioned specifically within that, but it was enough to raise awareness.”

The spate of threats recalls successive waves of bomb threats made against JCCs and other Jewish institutions in 2017, many of which led to evacuations of the buildings. Most of those threats came from a 19-year-old American-Israeli citizen, Michael Kadar. Last year, Kadar was sentenced to 10 years in prison.

Kadar also made hundreds of bomb threats to hospitals, airlines, schools and Jewish institutions in the United States, Canada, New Zealand, Australia and Britain.

“Yesterday, there were some similarities,” Hull said regarding the threats received by her JCC in 2017 and this year. “But it wasn’t anything that got me riled.”

According to Albany Police Department spokesman Steve Smith, the Albany JCC was evacuated for a couple of hours while officers did a sweep of the building. Smith said that the JCC received a “generic email” that mentioned a bomb. Police will be present at the building for the near future when parents drop off and pick up their children.

The Levin Jewish Community Center in Durham, North Carolina also received a bomb threat.

New York Governor Andrew Cuomo visited the JCC, which is in New York’s state capital, to show support.

“When you threaten a JCC, these are, it’s not just an anti-Semitic attack. You have children who go to the JCC. You have gym facilities here. So, you are really threatening children,” the governor said. “It is one of the most heinous things you can do. And again, it is fear and it is terror. That is all it is – terror.”