(WASHINGTON) -- On the first day of Black History Month, several historically Black colleges and universities were forced to temporarily cancel classes after receiving bomb threats, according to authorities and the schools. No bombs have been found and several universities have since given the "all clear" to students and faculty Tuesday.
At least 12 campuses were threatened, including Howard University, Alcorn State University, Coppin State University, Edward Waters University, Fort Valley State University, the University of the District of Columbia, Morgan State University, Kentucky State University, Xavier University of Louisiana, Philander Smith College and Arkansas Baptist College and Jackson State University.
"The Jackson Police Department and JSU Department of Public Safety have swept the campus and found the threat unsubstantiated. An all-clear has been issued," Jackson State University said in a statement Tuesday. "The campus will remain open with a heightened presence of law enforcement as a precautionary measure."
This is the third time within a month that HBCUs have been the subject of threats. No bombs or weapons have been found on campuses and no arrests have been made.
The FBI said Monday it is aware of the series of threats and is working with law enforcement to find the culprit.
“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 acting deputy director of the Bureau of Alcohol, Tobacco, Firearms & Explosives, Thomas Chittum, also said that agents from the bureau are responding to the reports.
"We can confirm that ATF has responded," Chittum told reporters on a call Monday. "Of course, it is a federal crime to use interstate facilities to make a bomb threat, and so ATF will provide our investigative expertise and support to that investigation, but obviously, the facts are preliminary and unfolding."
Judson University, which is not an HBCU, was also targeted.
Editor's note: ABC News incorrectly listed the HBCUs targeted with bomb threats Monday. Judson University was included but it is not an HBCU, however, it was also targeted.
ABC News' Alex Mallin and Luke Barr contributed to this report.