ROCK SPRINGS, Wyo. (AP) — Two Wyoming residents are trying to end the use of a gas chamber for euthanasia at an animal shelter.

The Humane Society of the U.S. says Wyoming is one of just four states where shelters still use gas chambers rather than lethal injection to euthanize animals; the others are Missouri, Ohio and Utah.

Animal welfare advocates say gas chambers are cruel because death often doesn't happen quickly.

The Rock Springs Rocket-Miner reports Madhu Anderson and Eve Waggoner have been protesting the use of gas at the Rock Springs animal shelter. Anderson says lethal injection is more humane and not difficult to implement.

Rock Springs Police Chief Dwane Pacheco says the shelter only euthanizes feral cats and aggressive dogs and has one of Wyoming's few free spay-and-neuter programs.

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