Amid visible incidents of anti-Semitism across the Twin Cities in recent months, federal authorities now believe the ongoing wave of bomb threats to Jewish Community Centers to be the work of a single person using voice-masking technology.

Speaking to reporters at the St. Paul Jewish Community Center Wednesday before a private meeting with area Jewish leaders, FBI Special Agent in Charge Richard Thornton said the same person is likely behind the bomb threats called in to the center last month and to the Sabes JCC in St. Louis Park in January.

The two bomb scares are part of a persistent rise in hate crimes targeting the local Jewish community that has mirrored events nationwide and prompted renewed assessments of security measures.

“People are trying to instill fear and terror in our communities,” said St. Paul Police Chief Todd Axtell, who lives a block away from the St. Paul JCC and is among its members. “I just can’t believe we are at a time in our society where this continues to occur throughout this country.”

Since the beginning of the year, Thornton said, the FBI has tallied more than 140 telephonic threats made to JCCs and other Jewish facilities in at least 43 states and overseas. Thornton said the caller specifically referenced planting C-4 explosives in the buildings, but authorities have not recovered any explosive materials from the targeted JCCs. The FBI is investigating the threats as a federal hate crime based on religious bias and is using cyber investigators and behavioral analysts.

Thornton said an additional 20-plus e-mailed threats have been sent to Jewish institutions, but none so far in Minnesota.

Wednesday’s meeting marked the first public appearance of Acting U.S. Attorney Greg Brooker since Andrew Luger was asked to resign late last week. Brooker pledged to continue working with the FBI on hate crime investigations: “It’s full speed ahead.”

Luger was originally scheduled to be on the panel but will still participate in a March 30 discussion at Temple Israel in Minneapolis with a former Nazi white supremacist who founded an organization that works to reform radicals.

Officials on Wednesday continued to plead that all threats be taken seriously and urged community members to report any suspected hate incidents — a trend Axtell said continues to go “very much underreported.” By the local Jewish Community Relations Council’s (JCRC) count, Minnesota is in the midst of a surge: the council tracked 21 anti-Semitic incidents last year, up from 12 in 2015. It has since counted eight so far this year.

The trend has taxed the security apparatus of local Jewish institutions but hasn’t caught them flat-footed, JCRC Executive Director Steve Hunegs said. The January bomb threat at Sabes JCC also prompted an outpouring of support from the local interfaith community and 22 Muslim organizations signed a letter of support published in the Star Tribune after last month’s threat in St. Paul.

“It’s a victory when people demonstrate resolve in the face of these threats,” Hunegs said. “These are the crossroads for the community and the last thing we want to do is to deny access to people.”

Hunegs said Wednesday that the JCRC, a public advocacy group that also serves as a liaison with law enforcement, is also advocating for legislation that would create a security fund for nonprofits.

Lon White, chief counsel for security and resiliency at the Sabes JCC, said the center routinely organizes safety drills for members as part of an “all hazards program.”

“We worked very hard to make it a very routine thing for them so it feels as non-disruptive as possible,” White said. “The people who feel the most impact are the parents, especially those with small children.”

The federal response to the bomb threats contrasts with President Trump’s reported suggestion that the threats could have been orchestrated by political opponents in an effort “to make others look bad.”

“We’re not in the business of advancing theories,” Thornton said. “We gather the facts, we gather the evidence and it leads us where it leads us.”