(CNN) — Eleven soldiers at Fort Bliss “fell ill after consuming a substance acquired outside of authorized food supply distribution channels,” a statement from the Army base said Friday.

In an email to CNN, the public affairs office for the base said the “substance ingested has not been revealed to us, as the investigation is ongoing.”

Located in El Paso, Texas, Fort Bliss is home to the 1st Armored Division, “America’s Tank Division.”

The unit was undergoing a field training exercise Thursday when the incident happened.

“We took immediate action to treat everyone involved with the best medical care available,” Maj. Gen. Sean C. Bernabe, senior mission commander of the 1st Armored Division and Fort Bliss, said in the statement.

The soldiers are receiving care at the William Beaumont Army Medical Center. Two remain in critical condition.

“Medical professionals are working hard to attend to the injured and provide all available aid,” Fort Bliss Public Affairs told CNN.

The incident was reported in a news release Thursday from Fort Bliss Public Affairs.

“Fort Bliss is investigating an incident involving 11 Fort Bliss Soldiers injured after ingesting an unknown substance during a field training exercise, today,” Fort Bliss Public Affairs said in the release.

Fort Bliss and law enforcement officials continue to investigate and plan to release more information Friday.

CNN has also reached out to the Department of Defense.

This story has been updated with a statement from Fort Bliss.

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