A suspicious package that contained white powder was delivered to a U.S. military base in Maryland, resulting in people becoming ill and some of them needing to be hospitalized, CNN reported yesterday, Thursday.

A building on the base was evacuated after a person “opened a suspicious package,” CNN reported, citing a statement from Joint Base Andrews, which is located outside the capital Washington.

“As a precaution, that building and another building connected to it were evacuated and the area was cordoned off,” the statement said.

Several people were transported to the Malcolm Grow Medical Center on the base, CNN reported. The extent of their illness was not made public.

Andrews base is known as the base of Air Force One, the aircraft used by the president of the United States.

The package contained an unknown white powder, CNN reported citing two sources.

Rapid response teams at Joint Base Andrews determined that there was no immediate threat and handed the case over to the Office of Special Investigations (OSI), CNN reported.

An initial field test by the hazardous materials (HAZMAT) team did not detect anything dangerous, but the investigation is continuing, CNN added, citing one of the sources.

CNN reported that the room where the envelope was opened — which is located in a building housing the Air National Guard Readiness Center — was closed off.

The Pentagon and Andrews base did not immediately respond to a Reuters request for comment. Reuters notes that it was not immediately able to confirm CNN’s reporting.