UMATILLA (AP) — The Army says it has destroyed the last nerve-gas weapon at the Umatilla Chemical Depot.

The depot can now begin disposing of mustard blister agent, the last of the chemical munitions to be destroyed at the Umatilla base.

The depot was established in the early 1940s, and chemical weapons have been stored there since 1962.

Under an international treaty, the depot began destroying nerve-gas munitions in September 2004. Destruction of land mines armed with VX, the last of the nerve gas weapons, began in September of this year.

About one milligram of VX can kill a person by disrupting the nerves that control breathing.

The transition to incinerating mustard gas, a nonexplosive weapon, will take about five months. The destruction is expected to take a year or two.