Israeli police on Thursday arrested a young man with dual U.S. citizenship in connection with a wave of threats to Jewish communities and institutions in the United States and other countries, according Israeli authorities and the FBI.

Authorities said the 19-year-old suspect, who lives in the southern Israeli city of Ashkelon, appeared to be behind the bulk of the recent threats, though it was unclear exactly how many.

Israeli police said in a statement that the cyberattack squad of its fraud unit had worked with the FBI and police organizations from other countries to track the suspect, whom they identified as Jewish. A motive was not immediately clear.

The suspect is thought to have used advanced camouflage technologies when contacting the institutions and making the threats, Israeli police said. A U.S. official, who spoke on the condition of anonymity to discuss the ongoing criminal investigation, said those tools would complicate the prosecution in the case.

The suspect appeared in court on Thursday, and Israeli cyber police requested that he be held in custody for at least another week. The court issued a gag order, which prevented authorities from revealing the young man’s identity.

The Jewish Community Center in Rochester, N.Y., was shut down because of a bomb threat on March 12. (Olivia Lopez/AP)

The FBI declined to release the man’s name because he remains in Israeli custody and had not been charged with U.S. crimes. The FBI said the suspect lived primarily in Israel and that it does not think he is linked to the vandalism of headstones at Jewish cemeteries in the United States.

Attorney General Jeff Sessions said in a statement that the arrest was “the culmination of a large-scale investigation spanning multiple continents for hate crimes against Jewish communities across our country.”

“The Department of Justice is committed to protecting the civil rights of all Americans, and we will not tolerate the targeting of any community in this country on the basis of their religious beliefs,” he said.

Jewish communities across the United States have been shaken by the threats against schools and institutions, which have fed into heightened anxieties about anti-Semitism.

The threatening messages, delivered through phone calls and emails, have forced a steady stream of evacuations from Jewish Community Centers, offices, day cares and school buildings.

The Anti-Defamation League said that as of this week, 166 threats had been made in 38 states as well as three Canadian provinces. That tally included five ADL offices that received bomb threats. In a statement Thursday morning, the ADL said it was “relieved and thankful to law enforcement” for the arrest.

Earlier this month, law enforcement officials charged a former journalist, Juan Thompson, 31, with making at least eight threats as part of a campaign to harass a woman.

(Thomas Johnson,Jenny Starrs/The Washington Post)

The FBI said it did not think Thompson was behind all the calls, nor did it think he was responsible for the vandalism at Jewish cemeteries in Philadelphia and near St. Louis.

[Former journalist arrested, charged with threats against Jewish facilities]

A new wave of threats to Jewish facilities followed days after Thompson’s arrest, prompting all 100 U.S. senators to sign a letter urging the Trump administration to take “swift action with regard to the deeply troubling series of anonymous bomb threats.”

These threats have come amid reports of a rise in anti-Semitism incidents and a surge in hate groups.

During a speech to Congress last month, President Trump said that the threats and the fatal shooting of an Indian man in Kansas were reminders that “while we may be a nation divided on policies, we are a country that stands united in condemning hate and evil in all its forms.”

Trump had been criticized for declining to condemn the anti-Semitic threats. He also unsettled Jewish groups and some public officials when he suggested to a gathering of state attorneys general in Washington that the threats might be coming from people seeking to make him or his supporters look bad.

Trump condemned the threatening messages during this meeting but said that they sometimes can be made in “the reverse,” according to two people who attended.

A White House spokeswoman did not immediately respond to a request for comment about the arrest Thursday.

Israeli police were first alerted to the possibility that the person behind the attacks was in their jurisdiction after a bomb threat at a Jewish institution in New Zealand in 2016. Police in New Zealand identified the IP address as originating from Israel, the Israeli newspaper Haaretz said.

Reports of threats at 16 Jewish centers in nine U.S. states soon followed — in Florida, New Jersey, Delaware, Maryland, Tennessee, Georgia, Pennsylvania, South Carolina and North Carolina.

Delta Air Lines also received a bomb threat, forcing it to make an emergency landing.

The FBI handed over the information to the Israeli police after finding that the threats had originated in Israel, Haaretz reported.

Doron Krakow, chief executive of the Jewish Community Center Association of North America, said the group was hopeful the period of disruption and concern had come to an end.

However, he said, “we are troubled to learn that the individual suspected of making these threats ... is reportedly Jewish.”

Zapotosky reported from Washington. Mark Berman in Washington contributed to this report.