ST. LOUIS -- The parents of a Missouri National Guard soldier who died of an ailment he contracted in Iraq say the Army has ruled out contact with chemicals.

Spc. Joshua Neusche, 20, of Montreal, died July 12 at a hospital in Germany. His parents say the Army surgeon general's office has told them the soldier probably died of a combination of Adult Respiratory Distress Syndrome and a rare form of pneumonia.

The military said last month it was investigating 19 cases of severe pneumonia since March, including the deaths of Neusche and Army Sgt. Michael L. Tosto, 24, a tank driver from Apex, N.C..

Tosto died June 17 from pneumonia that developed rapidly and killed him before he was airlifted from Baghdad to Germany.

The Army said last month the remaining 17 affected troops had been released from the hospital.

Four of the 19 cases were linked to bacterial infections and 10 patients, including Neusche and Tosto, had elevated levels of white blood cells called eosinophils. The cells are associated with a wide range of conditions, including allergies and parasitic infections.

His parents, Mark and Cindy Neusche, reported their conversation to the Missouri National Guard, which issued a press release on Friday.

Neusche's father said he accepted the Army's explanation of the soldier's death.

"We know that the Army and National Guard have done everything they could possibly do," the Guard quoted the father as saying. "We may never know exactly why this happened, but I just want to thank everyone who was there for us."

The Neusches did not immediately return a phone message left Saturday by the Associated Press.