Catholic University students were told for a time early Tuesday morning to shelter in place while authorities checked into an unconfirmed report about someone on campus who was possibly armed.

The order to shelter in place was issued on the university’s Facebook site and by Twitter. Although the timing of the university’s messages could not be precisely determined, it appeared that the first Twitter message from CU calling for students to take shelter may have been issued as early as midnight with the Facebook messages possibly issued later.

By about 2:40 a.m., the shelter order was rescinded, the university said in its Twitter feed.

The 2:40 a.m. message said members of the university community “may resume normal activities.” It said D.C. and campus police had concluded their search and determined that the campus was safe.

Earlier, in a Twitter message, the university had said the individual being sought was described as a tall, “middleeastern man, slim, wearing suit jacket.”

The vigorous response to the report and the seriousness with which it was taken appeared at least in part to reflect heightened concern over recent mass shooting incidents.

D.C. police said an initial report was received about 10:40 p.m. Monday apparently about someone who may have been armed at the university. In addition, police said early Tuesday that they were checking into a report of a suspicious package at the university, which is located in Northeast Washington. The precise timeline was somewhat unclear.

As of three hours later, nothing had been found, police said.

The university said the incident was touched off when a custodial worker reported being approached by a man with a weapon. The man reportedly approached the worker at Pangborn Hall about 10:30 p.m. Monday and asked directions to the administration building, then left after being given directions to Leahy Hall.

According to another online report, students in the campus library were escorted to their residences by police. The late night population at the library included students cramming for final exams.

At about 1:50 a.m., Facebook provided an update.

It said: “Shelter in place is still in place. Our priority is your safety. We will share details as they’re available.”

This story has been updated.