Eleven Fort Bliss soldiers are injured after having ingested an “unknown substance” during a training exercise, according to a press release from Fort Bliss’ 1st Armored Division shared Thursday.

Two of those soldiers are currently in critical condition.

Officials at themilitary base in Texas are investigating the incident, the release states, but few details are known at this time.

“All members involved in the incident are under observation of medical professionals,” the press release says. “Fort Bliss officials will provide updates as more information becomes available.”

The 1st Armored Division — also known as “Old Ironsides”– is a renowned U.S. Army armored division consisting of approximately 17,000 highly-trained soldiers, according to the Army’s website.