An envelope containing a suspicious letter was opened at a US military base near Washington, leaving 11 people including nine Marines sick.
A gunnery sergeant opened the envelope received yesterday at Joint Base Fort Myer-Henderson Hall in Arlington, Virginia.
People who were exposed reported symptoms including itchy hands and faces and bloody noses, a Marine official told NBC News. The building was evacuated immediately.
The official said the envelope was addressed to the Marines' headquarters battalion on the base, not to an individual.
"Shortly after receiving the letter, 11 people started to feel ill and caused the evacuation of the building," Major Brian Block, a Marine spokesman said.
After the evaluation of 11 people, three personnel were transported in stable condition for further medical evaluations.
The building was screened and cleared.
"The letter was removed, and NCIS (Naval Criminal Investigative Service) and FBI are conducting a joint investigation," he said.
Fort Myer is adjacent to Arlington National Cemetery and is jointly controlled by the Army and Marine Corps. It is also home to the Army's Third Infantry Regiment, known as the Old Guard, which serves as the presidential honour guard.