Eleven soldiers were poisoned after drinking a beverage they mistook for alcohol during a training exercise at a Texas Army base on Thursday, officials said.

The soldiers are suffering from ethylene glycol poisoning, Lt. Col. Allie Payne, a spokesperson for Fort Bliss' 1st Armored Division, said during a press briefing Friday afternoon.

Ethylene glycol is found in consumer products like antifreeze and hydraulic brake fluid.

As of Friday, two of the soldiers previously listed in critical condition have improved but remain seriously ill in the intensive care unit, Payne said. By Saturday afternoon, five soldiers were set to be released from the non-critical care ward, officials said. "All continue to gain improved health," the 1st Armored Division tweeted.

Those harmed include one warrant officer, two noncommissioned officers and eight enlisted members, officials said. All have been under observation at William Beaumont Army Medical Center since Thursday afternoon.

The incident occurred on the final day of a 10-day field training exercise on Fort Bliss’ McGregor Range complex. The soldiers thought they were drinking an alcoholic beverage, Payne said.

Army personal are prohibited from drinking alcoholic beverages while on duty and while in a training environment. The U.S. Army’s Criminal Investigation Command is investigating how the soldiers came to ingest the substance and if there should be any disciplinary action, Payne said.

The Fort Bliss' 1st Armored Division initially said the soldiers became sick after ingesting an "unknown substance," according to a statement released Thursday. In an update Friday morning, officials described the substance as "acquired outside of authorized food supply distribution channels."

"The circumstances of how the Soldiers ingested the substance are under investigation by the U.S. Army Criminal Investigation Command (USACIDC). There is no reason to believe there is any threat to the greater Fort Bliss community," Fort Bliss' 1st Armored Division said in a statement Friday night. "The Fort Bliss senior commander has also directed an administrative investigation to determine the facts and circumstances that led to yesterday’s events."

The 1st Armored Division -- also known as "Old Ironsides"-- is a renowned armored division, consisting of approximately 17,000 highly trained soldiers, according to the Army's website. (Text, excluding headline, courtesy ABC News)

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