Eleven people at a US military base in Arlington, Virginia fell ill and three were taken to a hospital on Tuesday after a letter was opened in the Marine Corps’ portion of the base, the fire department and a base spokeswoman said.
Leah Rubalcaba, a spokeswoman for Joint Base Myer-Henderson Hall said everyone at the office started feeling bad soon after someone opened a letter.
The three people taken to a hospital were in stable condition, Arlington Fire Department said on Twitter.
“An envelope containing an unknown substance was received” at the base, the Marine Corps said in a statement.
The building was ‘screened and cleared’ and the letter removed, reports Reuters citing the statement.
The Naval Criminal Investigative Service and the Federal Bureau of Investigation are conducting a joint investigation.