The Arlington County Fire Department’s hazmat team is investigating a suspicious substance at a federal office in Shirlington.

Hazmat personnel are preparing to enter an office at 2800 S. Randolph Street, according to scanner traffic. They will be performing tests on the substance to determine whether or not it is hazardous.

Among the tenants listed for the 2800 S. Randolph Street building, also known as Randolph Square, is the U.S. Patent and Trademark Office.