Buildings at a Baltimore hospital were evacuated Thursday after employees were possibly exposed to tuberculosis, officials said.

The Baltimore City Fire Department responded to Johns Hopkins Hospital to investigate after “a small sample of frozen tuberculosis” being used for research purposes was inadvertently released in an internal bridge between Cancer Research Building 1 and Cancer Research Building 2, Johns Hopkins Medicine spokeswoman Kim Hoppe said in a statement.

Employees were in the area, which does not connect to the hospital, during the incident and were isolated. No information about their condition was immediately available.

Both cancer research buildings were evacuated, according to the statement, and there was no indication that others were exposed. At about 4:45 p.m., officials said, the evacuation was finished.

Baltimore fire officials were not immediately available for comment.