Israeli police have arrested a 19-year-old Israeli Jewish man as the primary suspect in a string of bomb threats targeting Jewish community centers and other institutions in the U.S.

Police spokesman Micky Rosenfeld described the suspect as a hacker but said his motives were still unclear.

Israeli media identified him as an American-Israeli dual citizen and said he had been found unfit for compulsory service in the Israeli military. His name wasn't released.

The Anti-Defamation League says there have been more than 150 bomb threats against Jewish community centers and day schools in 37 states and two Canadian provinces since Jan. 9.

In Florida, the Jewish Community Center of Greater Orlando had to be evacuated three times in January because of bomb threats.

Police didn't list the specific cases involving the 19-year-old suspect.

The threats led to criticism of President Donald Trump’s administration for not speaking out fast enough. Last month, the White House denounced the threats and rejected “anti-Semitic and hateful threats in the strongest terms.”

U.S. authorities have also arrested a former journalist from St. Louis for allegedly threatening Jewish organizations. Juan Thompson has been indicted in New York on one count of cyberstalking.

But Israeli police described the local man as the primary suspect in the wave of threats.

Israeli police said the suspect made dozens of calls claiming to have placed bombs in public places and private companies, causing panic and “significant economic damage,” and disrupting public order, including by the hurried evacuations of a number of public venues around the world. The man is suspected of placing threatening phone calls to Australia, New Zealand and also within Israel.

“He didn’t use regular phone lines. He used different computer systems so he couldn’t be backtracked,” Rosenfeld said.

The Associated Press contributed to this story.