At least 12 white supremacists have been arrested since Pittsburgh shooting: ADL The Jewish organization compiled some concerning numbers.

Jewish communities in the U.S. continue to face threats as the anniversary of the deadliest attack on Jews in the nation approaches.

According to a new report from the Anti-Defamation League, a Jewish organization focused on fighting anti-Semitism, at least 12 white supremacists were arrested for plots, attacks or threats against Jews since the deadly shooting in Pittsburgh on Oct. 27, 2018.

The ADL list includes some incidents where the suspect's alleged white supremacist ties have not been independently verified by ABC News. But several of the incidents – including the deadly shooting at a California synagogue, or the thwarted threat against an Ohio synagogue, among others – have been confirmed by ABC News reporting.

"It is horrifying that in the year since the deadliest anti-Semitic attack in U.S. history, at least a dozen white supremacists were arrested after threatening to target Jewish houses of worship," ADL CEO Jonathan Greenblatt said in a statement.

Greenblatt also said the ADL's Center on Extremism shared information connected to the investigations and arrests with law enforcement on at least three of the 12 cases.

"We cannot and will not rest easy knowing the threat posed by white supremacists and other extremists against the Jewish community is clear and present. We are proud of our collaborative efforts with law enforcement to prevent such tragedies from taking place and ensuring would-be perpetrators of these heinous crimes are brought to justice," Greenblatt said.

There have been 780 anti-Semitic incidents in the first six months of 2019, just shy of the 785 incidents reported in the first six months of 2018, according to the report.

The report, first released on Friday, said seven additional white supremacists who were targeting other groups and not Jews have been arrested since the Pittsburgh shooting.

The report states that those suspects' alleged "targets were varied, to say the least, ranging from large retail stores and hospitals to night clubs and news stations."