The U.S. Federal Bureau of Investigation (FBI) has identified six “tech savvy” minors as persons of interest in bomb threats to historically Black colleges and universities (HBCUs).

According to NBC News, a law enforcement official says the six juveniles were located across the country and allegedly used sophisticated techniques to try to conceal the source of the threats, which seemed to be racially motivated.

As REVOLT previously reported, the first round of bomb threats came at the beginning of last month. Officials at the University of Arkansas at Pine Bluff, Howard University, Norfolk State University, Xavier University, North Carolina Central University, Florida Memorial University and Prairie View A&M University notified authorities about the bomb threats at their schools and ordered students and faculty members to evacuate or shelter in place.

After an initial investigation, no active devices or explosions were found. All-clear notices were sent out and students who left campus returned to their dormitiories.

The second round of bomb threats came at the end of last month and were made toward six HBCUs. The FBI released a statement confirming their knowledge of the threats. “As always, we would like to remind members of the public that if they observe anything suspicious to report it to law enforcement immediately,” the FBI said in a statement to ABC News.

The third round of threats coincidentally fell on the first day of Black History Month. More than a dozen HBCUs, including Mississippi Valley State University, Alcorn State University, Tougaloo College, Kentucky State University, Fort Valley State University, received bomb threats and were forced to lock down or postpone classes.

“Due to a bomb threat, access to campus will be closed as the University works with emergency personnel to assess the situation,” Morgan State University tweeted on Tuesday morning (Feb. 1). “Everyone on campus should shelter in place until further notice. All instruction will be remote and all employees should telework.”

No active devices or explosives were found.