Commonwealth Avenue is being reopened after police converged on Boston University Friday morning following a report of an armed man with hostages and suspicious devices.

Police believe the emergency was a hoax, according to school officials.

The threat, which was not a robocall, claimed to be from a gunman on the fourth floor of Mugar with hostages and explosives, Boston Police Commissioner Bill Evans told reporters.

The caller claimed to have booby traps and called police a second time saying that he had shot a hostage, according to WBUR.  

Authorities briefly closed off and evacuated the area around 771 Comm Ave., where the school's student union and library are located, after the call was made.

The Boston Police Department's bomb squad was on the scene before 9.

About an hour later, BU posted on its Twitter acount that the area was clear and there was no threat.

The street was later reopened.

Karen Weintraub, a BU professor and journalist, tweeted around 8:45 a.m. that something "serious and scary" was happening near BU's student union. She said there were "at least a dozen cop cars" out front and that one of the officers entered the building with a rifle.