NEW YORK (Reuters) – More than a dozen Jewish community centers around the United States and one in Canada received bomb threats on Tuesday, the third wave of threatened attacks against them this month.

A total of 14 centers across 10 states, along with one in Canada, received the threats, according to David Posner, a director at the JCC Association of North America who advises centers on security.

He said most of the centers had received the all-clear from law enforcement officials and had resumed regular operations, though security was heightened.

“We are concerned about the anti-Semitism behind these threats,” Posner said in an emailed statement. He added that the previous threats phoned in this month were deemed to be hoaxes and that no one has been injured.

Jewish community centers in California, Colorado, Illinois, New Jersey, New Mexico, New York, Massachusetts, Ohio, Utah, Wisconsin and Ontario, Canada received the threats, according to the statement.

Telephoned threats on Jan. 9 were made against 16 Jewish community centers in nine U.S. states, and a second wave on Jan. 18 targeted 27 centers in 17 states.

Some of the calls were made using an automated “robocall” system, while others were made by individuals, security officials have said.

After the second round of threats, the FBI said that it and the Justice Department were investigating possible civil rights violations in connection with threats. No arrests have been made.

(Reporting by David Ingram; additional reporting by Curtis Skinner; Editing by Sandra Maler and Dan Grebler)