(Reuters] – Tuesday was a busy day for Black colleges and universities across the United States. It came after a rash if similar threats to other schools forced them to cancel classes.

According to local media and Twitter postings, Howard University (Washington), University of the District of Columbia as well Kentucky State and Xavier University of Louisiana were some of the schools reported receiving threats.

Campus is currently under lockdown. Residential students remain in dorms. Nonresidential staff and students should not be reported to campus without further notice. “Campus operations have been suspended until further notice,” Fort Valley State tweeted.

After receiving a threat around 2:55 AM, Howard was given the all-clear Tuesday morning. It posted the tweet on Twitter.

After similar threats, several other HBCUs instructed students and staff to stay put and cancelled classes on Monday. Schools were allowed to reopen because authorities didn’t find any suspicious objects.

The FBI released a statement Tuesday saying that it was aware of the bomb threat in the United States and is working closely with law enforcement partners. It encouraged citizens to inform the FBI if there is anything suspect.

Louisiana’s Xavier University students were instructed to remain in their dormitories until further notice, and to keep an eye on university channels.

“ALERT! XULA has received a bomb threat & is working w/ authorities. The school tweeted that Campus would be out of reach until noon.