WASHINGTON – For the second time in a little more than a week, an unknown substance was found in the incoming mail at the D.C. Department of Corrections facility in Southeast, and a worker there has been taken to a hospital.

Department of Corrections spokeswoman Keena Blackmon said in a statement Friday afternoon that the substance was found in incoming mail at the Correctional Treatment Facility, on E Street in Southeast.

The worker was taken to a hospital as a precaution, Blackmon said; three others who may have been exposed to the substance were treated at the site.

On March 15, seven workers at the facility were taken to a hospital, and nine others treated, after another suspicious substance was found in the incoming mail. The substance was tested and originally thought to be fentanyl, but turned out to be synthetic cannabis.