• A suspicious letter was opened at Joint Base Myer-Henderson Hall in Virginia on Tuesday that caused 11 people to suddenly feel ill.
• Three Marines were hospitalized but were released late Tuesday night.
• The building has also been cleared and is operational.
• The letter has been sent to an FBI lab in Quantico for further study, and the FBI and NCIS will conduct a joint investigation into the incident.

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The Marine Corps confirmed Wednesday that Joint Base Myer-Henderson Hall has been cleared after 11 people showed symptoms after opening a suspicious letter.

Three Marines that were hospitalized were released late Tuesday night.

“The building is cleared and it is operational today,” a spokeswoman for the Marine Corps told Business Insider. “We are waiting on the FBI and the NCIS for further information.”

The incident happened Tuesday when a Marine at Joint Base Myer-Henderson Hall, which is located near the Pentagon in Virginia, opened a letter which contained an unknown substance.

“An envelope containing an unknown substance was received, today, aboard Joint Base Ft. Myer-Henderson Hall. Personnel in the affected building took immediate preventative measures by evacuating the building,” Maj. Brian Block, a US Marine Corps spokesperson, said.

Eleven people reported feeling ill after the letter was opened. The symptoms reportedly included burning sensations on their hands and face, and at least one person had a nosebleed.

The entire building was evacuated, and local HAZMAT teams arrived along with the Arlington Fire Department.

Authorities have not released what the substance inside the letter was, but it has reportedly been sent to an FBI lab in Quantico, Virginia. The FBI, along with the Naval Criminal Investigative Service, the Navy’s primary law enforcement agency, are expected to conduct a joint investigation.

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