One Schofield Barracks soldier was in critical condition and three were in stable condition yesterday from what the Army for the first time revealed was the explosion of an 81 mm mortar round Friday at Pohakuloa Training Area on the Big Island.

"The cause of the explosion and what the soldiers were doing at that exact time of the explosion are still the subject of investigation," the Army said in a release.

Staff Sgt. Oscar Rodriguez, 27, a native of Beeville, Texas, was killed during the training. A memorial service will be held tomorrow at Schofield Barracks.

The Combat Readiness Center out of Fort Rucker, Ala., and CID, the Army's criminal investigative organization, are looking into the explosion as part of separate investigations, an Army official said.

Rodriguez was assigned to the 25th Infantry Division's 1st Battalion, 14th Infantry Regiment. Although 7,000 Scho-field Barracks soldiers are preparing for a summer deployment to Iraq, 1-14 is not among those with deployment orders, an official said.

Rodriguez was killed and the other soldiers were injured during a live-fire training exercise, the Army said.

The Hawai'i County Fire Department previously had said all "sustained blast trauma due to accidental munitions malfunction."

Yesterday's Army news release for the first time identified the munition involved in the accident.

An Army Black Hawk helicopter took Rodriguez to Hilo Medical Center, where he was pronounced dead. The other soldiers also were taken to Hilo Medical Center.

One soldier in stable condition has been transferred to Tripler Army Medical Center. The three others, including two in stable condition and one in critical condition, were at The Queen's Medical Center. The two in stable condition were being prepared to be moved to Tripler.

Rodriguez joined the Army in 1996 and was assigned to Schofield in October 2002. He is survived by his wife and son.

Monday evening, a large American flag hung outside the family's Makakilo townhouse. Friends and a casualty assistance officer were with Rodriguez's wife.

The Army's Combat Readiness Center, formerly known as the Army Safety Center, has primary responsibility for the investigation of Army accidents.

The Army suspended live-fire training at Pohakuloa after the accident. Pohakuloa Training Area consists of 109,000 acres near the center of the Big Island. It is used to train ground troops and aircraft units.

Task Force Wolfhound recently deployed more than 530 soldiers to Pohakuloa and trained with live-fire, including small arms and mortars. Schofield soldiers increasingly have trained at the sprawling base because of a ban on live fire at Makua Valley on O'ahu.

The last fatal training accident for the Army at Pohakuloa occurred April 12, 2000, when Spc. Don Falter, 21, was killed and four other soldiers were injured when a "bangalore torpedo" used to clear concertina wire exploded.

Reach William Cole at wcole@honoluluadvertiser.com.