D.C. police are interviewing a person on Tuesday in connection with a white powder, initially believed to be ricin, found in a student dormitory at Georgetown University, according to campus and District authorities.

Officer Araz Alali, a D.C. police spokesman, said preliminary tests on the powder were negative for ricin, but more tests are being conducted before a final determination is made. Police would not say why the powder was initially believed to be ricin.

Students were not forced to leave either McCarthy Hall, in the 3700 block of O Street NW, where the powder was found, or the campus. McCarthy Hall and two other dormitories in a singular complex hold up to 780 upperclassmen.

But Georgetown’s police chief, Jay Gruber, sent a campus-wide notice warning students that they’d likely see an increased presence of District police officers and federal authorities.

Alali said the initial call came in about 4:30 a.m. but he would not describe details of how the powder was found, or whether it was in an envelope that was sent to the dorm. Gruber said in his campus-wide e-mail that all tests for biological substances were negative, but cautioned that more work needs to be done before anything is ruled out.

Police would not describe the person they are interviewing as a suspect. They also would not say if that person is a student.

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