The Anti-Defamation League’s San Francisco office was evacuated following a bomb threat on Monday, one of more than 20 such threats made against Jewish institutions around the country in just one day.

The office was evacuated after a caller told a staff member at 4:19 p.m. local time that an explosive device had been hidden in the building.

More than 20 other anti-Semitic incidents, including bomb threats against Jewish schools and community centers, were reported around the US on Monday.

The incidents spanned 12 states, including Alabama, Delaware, Florida, Indiana, Maryland, Michigan, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island and Virginia.

ADL officials say the threats Monday constitute the fifth recent wave of bomb threats and other forms of harassment against Jewish institutions. Some 90 threats and attacks on Jewish cemeteries and community centers have been registered since the beginning of 2017.

“One threat or evacuation is one too many, and yet we’ve now seen more than 20 incidents in a single day not just to ADL, but to children's schools and community centers -- and more than 90 incidents since the start of this year,” said ADL CEO Jonathan A. Greenblatt. “The level of threats and incidents is astounding, and must not stand. We will do everything in our power to combat this wave of anti-Semitism.”

In addition to the recent rash of bomb threats, a number of Jewish cemeteries have been vandalized over the past two weeks.

Tombstones were destroyed in the Mt. Carmel Cemetery in Philadelphia on Sunday, days after a similar incident in the Chesed Shel Emeth Cemetery near St. Louis. Vice President Mike Pence visited the cemetery in St. Louis to show his support for the Jewish community there and said "There is no place in America for hatred or acts of prejudice or violence or anti-Semitism."