The Florida Department of Motor Vehicles building was evacuated Tuesday morning after a suspicious letter was received.
Some 1,500 employees were cleared out after a letter claiming to have a biological weapon was intercepted in the records room of the building, authorities said.
The building, located four miles east of the State Capitol, reopened around 1 p.m. after the Regional Domestic Security Task Force investigated found no harmful substance.
"Out of an abundance of caution, staff worked quickly in executing normal protocols of notifying authorities and clearing the building to ensure the safety of our employees," DMV executive director Julie Jones said.
The letter was placed in a sealed container and sent to a lab in Jacksonville, Tallahassee Fire Department Lt. Mike Bellamy said. Bellamy told reporters initial tests on the envelope were negative for a substance such as anthrax.
"There doesn't seem to be anything there," he told reporters..
Six employees who worked close to where the letter was found were examined and were cleared to return to work. The matter is being investigated by local state and federal law enforcement agencies.
The incident comes as Mississippi officials charged a new suspect with sending letters containing ricin to President Obama and others.