Eleven Fort Bliss soldiers have been injured after having ingested an”unknown material” through a practice exercise, according to a press launch from Fort Bliss’ 1st Armored Division shared Thursday.

Two of these soldiers are in critical illness.

Officials in themilitary base in Texas are investigating the incident, the release conditions, but a few details are known at the moment.

The 1st Armored Division — also called”Old Ironsides”– is now a renowned U.S. Army armored branch comprising roughly 17,000 highly-trained soldiers, according to the Army’s site .