A suspicious package was delivered to a US military base in Maryland on Thursday which caused multiple people to fall ill and be taken to the hospital, CNN has learned.

A statement from Joint Base Andrews, which is located outside Washington, DC, said that a building on the base was evacuated after an individual “opened a suspicious package.”

“As a precaution, the building and connecting building were evacuated, and a cordon was established around the area,” the statement said. “Joint Base Andrews first responders were dispatched to the scene, determined there were no immediate threats, and have turned the scene over to Office of Special Investigations. An investigation is currently ongoing.”

Several people were transported to the on-base Malcolm Grove Medical Centre after the package was opened, which contained an unknown white powder, two sources familiar with the investigation said.

One of the sources familiar said an initial field test from the HAZMAT team did not detect anything hazardous but the investigation remains ongoing. The HAZMAT team departed the scene on Thursday evening.

The extent of any illness reported by those in proximity to the package is not yet known.

The room where the envelope was opened – located in a building that houses the Air National Guard Readiness Center – remains closed.

Investigators are also assessing political propaganda that was included in the package, the two sources said.

Joint Base Andrews is the military base through which VIPs such as the president, vice president, and cabinet secretaries regularly travel on official business. President Donald Trump was at Joint Base Andrews on Wednesday.

The Air National Guard Readiness Center functions as a liaison between the National Guard Bureau and Air National Guard units in every state and territory. (CNN, but headline rejigged)