Navy: Initial tests on suspicious powder found in Virginia mailroom not toxic

Initial tests have come back negative for poisonous substance following a suspicious white powder found Thursday morning in the mailroom of the Naval Support facility in Arlington, Va.

About 800 people were evacuated after the powdery substance was found in the mailroom of Building  No. 12 at the support facility, the Navy said in a statement. All have since been let back in, Fox News has learned. 

Building 12 houses the mailroom and the offices of the chief of naval personnel, according to the official, who said the evacuations were a precautionary measure. The Arlington County Fire Department and hazardous-materials officials, as well as Navy personnel, are on the scene investigating. 

The incident comes just days after letters that tested positive for the poison ricin were mailed to President Obama and Sen. Roger Wicker, R-Miss, in Washington. The FBI arrested Mississippi resident Paul Kevin Curtis in connection with the letters Wednesday night, an FBI release said. Curtis is scheduled to appear in federal court Thursday and, if convicted, could face more than a decade behind bars.

Fox News' Justin Fishel contributed to this report.