The FBI has reportedly identified six "tech savvy" juveniles as persons of interest in the bomb threats sent to multiple historically Black colleges and universities (HBCUs) this week. 

A law enforcement official told NBC News that the individuals used sophisticated methods to try to hide the source of the threats and added that they seem to have a racial motivation.

The identities of the individuals have not been released. 

The FBI said in a statement to The Hill that the investigation is of the highest priority and involves "more than 20 FBI field offices across the country," adding that the threats are being investigated as "Racially or Ethnically Motivated Violent Extremism and hate crimes."

The FBI said that no explosive devices have been found at any locations, but that the agency is taking the threats "with the utmost seriousness."

Police first responded Monday when six HBCUs, including Howard University in Washington, D.C., received bomb threats against their campuses, leading to closures and lockdowns. The next day, the first day of Black History Month, at least 12 more institutions received similar threats. 

The FBI announced their investigation into the threats on Tuesday, stating that "we are working with our law enforcement partners to address any potential threats." 

White House press secretary Jen Psaki on Monday called the threats "disturbing," adding that President Biden was aware of them.