Law enforcement officials are investigating a ricin scare in a Georgetown University dorm, though the campus’ police chief said students were not in danger.

D.C. Fire and Emergency Medical Services responded to a call Tuesday morning for “a possible hazardous substance” in McCarthy Hall, Georgetown chief of police Jay Gruber said in an email to students, which was provided to The Hatchet.

Gruber said initial test results came back negative and students were not in danger if they remained in their dorms. A subject has been identified and police are conducting interviews.

“This is an active investigation so you may see an increased presence of law enforcement authorities on campus. The university is cooperating with local and federal authorities on this ongoing investigation,” he said.

Ricin is a highly toxic substance found in castor beans and can be deadly, according to the Center for Disease Control.