Twenty-seven Jewish community centers in 17 US states reported receiving false telephone bomb threats on Wednesday, prompting evacuations and an FBI probe into the second wave of hoax attacks to target American Jewish facilities this month.
The JCC Association of North America, a network of health and education centers, said the threatened organizations were working with police and many had resumed operations after no bombs were found nor injuries reported, as was the case after the earlier series of threats on January 9.
No one claimed responsibility for the calls on Wednesday nor nine days ago, and the Federal Bureau of Investigation (FBI) has not named any suspects nor described a likely motive.
The FBI and the Justice Department are investigating possible civil rights violations in connection with threats, the FBI said in a statement.
"The FBI will collect all available facts and evidence, and will ensure this matter is investigated in a fair, thorough, and impartial manner," the statement said.
In Miami Beach, Florida, a center received a call at 9:54am and was evacuated, police said on Twitter. Officers and police dogs searched the area but found no bomb and the center reopened, they said.
Two centers in Connecticut said on Facebook they had received threatening phone calls and had evacuated. No bombs were found, they said.
Centers in New York, New Jersey, Ohio, Massachusetts, Maryland, Michigan, Minnesota, Delaware, Alabama, California, Maine, Tennessee, South Carolina, Missouri, Texas and Kansas also received threats, according to the Anti-Defamation League (ADL).
ADL director Jonathan Greenblatt said that "so far these threats do not appear to be credible," but urged centers to take them seriously nevertheless.
"While each incident needs to be taken seriously and investigated closely, thus far we are not aware of any of these threats being substantiated," Greenblatt said.
The January 9 threats targeted 16 Jewish community centers in nine US states, prompting the FBI to look into the source of the calls, some of them made using an automated "robocall" system.
It was not immediately clear if there was overlap between centers that received calls on January 9 and those that received them on Wednesday, but the volume of threats was unheard of, said Paul Goldenberg, national director of the Secure Community Network, a nonprofit that advises Jewish groups on security.
"These are individuals or groups that want to disrupt our way of life," Goldenberg said, adding that they would not succeed. "We're not going to shut down institutions because of this."
After last week's threats, the JCC Association of North America trained staff and reviewed security plans, the group said.
"While we're extremely proud of our JCCs for professionally handling yet another threatening situation, we are concerned about the anti-Semitism behind these threats," David Posner, director of strategic performance at the association, said in a statement.
The Associated Press contributed to this report.