Harvard University has issued an all-clear for two of the four campus buildings evacuated because of a report of possible explosives. 

Fire truck in front an evacuated building at Harvard University (Twitter)The school tweeted that there have been no reports of any explosions.

Two of the evacuated buildings--Thayer and Emerson Hall -- have been deemed safe for return.

The other two buildings: Science Center and Sever, are still being investigated.

"There were 300 students in our constitutional law class who had just sat down for exams in the Science Center when fire alarms went off," junior Matt Wardrop told WCVB TV.

The school posted alerts on its emergency page and its Twitter account. They say that both school and city police are investigating, and the university will provide more information soon.

Harvard says in a statement that its university police department received the unconfirmed report that explosives may have been placed in the four buildings and they were evacuated out of an abundance of caution.

Massachusetts State Police are sending a bomb squad to the campus; the nearby Harvard MBTA transit station has already been checked.

Final exams have begun at the Ivy League school. Fox 25 in Boston reports nine final exams happening at 9 a.m. in the buildings being evacuated.


The Associated Press contributed to this report.