Eleven soldiers were injured after ingesting an unknown substance during a field training exercise at Fort Bliss in Texas, the US Army said late Thursday. Two of the soldiers were in critical condition, the 1st Armored Division said in a statement, reports the AP. All eleven were placed under the observation of medical professionals, states a press release. The incident is under investigation, the statement said. No further details were released. Per the Army's website, the 1st Armored Division is known as "Old Ironsides" and is made up of roughly 17,000 highly trained soldiers. (More Fort Bliss stories.)