The substance that prompted an evacuation of a Minneapolis apartment complex near the University of Minnesota on Tuesday, May 7, may indeed be ricin, according to preliminary tests by the Minnesota Department of Health.

The Marshall in Dinkytown was evacuated about 4 p.m. after authorities received a report that a female U student had been hospitalized after coming into contact with “a dangerous material that could have been ricin,” according to a news release issued Wednesday by the FBI.

A combined hazardous materials team from the FBI and the Minnesota National Guard collected the substance and processed the scene of the exposure, believed to have been limited to a single apartment in the building.

Read more: Duluth News Tribune