PUEBLO, Colo. (AP) — The Army says it has reached a milestone at a Colorado chemical weapons depot by destroying nearly 300,000 decades-old artillery shells containing mustard agent. Walton Levi, site project manager of the U.S. Army Pueblo Chemical Depot, made the announcement in a depot publication on Tuesday.

(credit: Pueblo Chemical Depot / Facebook)

Depot workers destroyed the last of the 155mm World War II-era shells on Saturday.

READ MORE: Mom Fights With Insurance Company To Get Disabled Daughter Wheelchair

Each shell contained nearly 12 pounds of mustard agent, which can maim or kill, blistering skin, scarring eyes and inflaming airways.

READ MORE: MSU Denver Offers COVID Vaccine Incentive With Scholarship Drawing

The plant started operating in 2016 with more than 780,000 munitions in its original stockpile containing 2,500 U.S. tons of mustard agent. It is eradicating shells under an international treaty banning chemical weapons with a 2023 projected completion date.

(credit: Bechtel.com)

Plant technicians will retrofit robots and other systems used to handle and destroy munitions before beginning work to eliminate 105mm projectiles with 3 pounds each of mustard agent.

MORE NEWS: COVID Vaccine: Denver Moves Focus From Quantity To Localized, Targeted Population

(© Copyright 2020 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)