Eleven soldiers were hospitalized at Fort Bliss in Texas after they drank antifreeze mistaken for alcohol, Army officials said Friday, as two service members remained in critical condition.

The soldiers were on the last day of a 10-day field training exercise when the incident occurred Thursday, Lt. Col. Allie Payne, a spokesperson for the 1st Armored Division and Fort Bliss, said during a news conference. Some soldiers may be released from the hospital later Friday, she said, noting that the two most serious cases required intensive care.

The substance detected in lab results – ethylene glycol – is commonly referred to as antifreeze, Payne said.

“The soldiers fell ill after consuming a substance acquired outside of authorized food supply distribution channels,” she said in an earlier statement. All but one of the soldiers were enlisted personnel, with one warrant officer among those injured.

Law enforcement is investigating the incident, Payne said.

Ingesting antifreeze can cause kidney damage, which could lead to organ failure, Col. Shawna Scully, deputy commander for medical services at the William Beaumont Army Medical Center at Fort Bliss, said during the news conference.

Army regulations prohibit soldiers from drinking alcohol while in the field. Payne did not indicate whether the soldiers confused the antifreeze with alcohol, or if it was deliberately mixed together to form a toxic cocktail. Bowls of alcohol with several spirits mixed together, known as grog, are mainstays at military social functions and sometimes include less-than-appetizing ingredients, such as hot sauce.

The soldiers all belonged to the 11th Air Defense Artillery Brigade, Payne said, which uses air artillery like the Patriot system to shoot down enemy rockets and missiles.

Fort Bliss has been scrutinized in recent weeks after the death of Pfc. Asia Graham, who was found unresponsive in a barracks on New Year’s Eve. She had previously reported another soldier for sexual assault. That soldier is facing a court-martial on the sex assault charge, CNN reported.