Sen. Elizabeth Warren, D-Mass., introduced a bill Wednesday that would posthumously revoke 20 Medals of Honor awarded to U.S. soldiers who slaughtered hundreds of Native Americans -- mostly women and children -- at the Wounded Knee Massacre of 1890.

The Remove the Stain Act accompanies a House version introduced earlier this year by Democrats Paul Cook of California, Denny Heck of Washington and Deb Haaland of New Mexico.

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“The horrifying acts of violence against hundreds of Lakota men, women and children at Wounded Knee should be condemned, not celebrated with Medals of Honor,” Warren said in a statement. “The Remove the Stain Act acknowledges a profoundly shameful event in U.S. history, and that’s why I’m joining my House colleagues in this effort to advance justice and take a step toward righting wrongs against Native peoples.”

The proposal is co-sponsored by Democratic Sens. Jeff Merkley and Ron Wyden of Oregon, Kamala Harris of California and Patrick Leahy and Bernie Sanders, the Vermont independent. Several Native American tribes, including descendants of the victims, have backed the legislation along with veterans groups such as VoteVets and Veterans for Peace.

Wounded Knee took place on Dec. 29, 1890 when U.S. troops with the 7th Calvary began to crack down on a religious movement known as the Ghost Dance. Lakota leader Chief Big Foot and his people were confined to a camp in South Dakota and ordered to give up their weapons.

When a weapon accidentally went off, the cavalry troops opened fire and killed as many as 250 people. Congress apologized for the massacre in 1990 but did not revoke the medals, the military's highest award.

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“The Medal of Honor is the highest award our nation can bestow upon its servicemembers for acts of valor," Heck said. "There was no valor in the killing of unarmed Lakota men, women, and children at Wounded Knee Creek in 1890, and the Medals of Honor given for the massacre must be rescinded."

Republican Sen. Mike Rounds of South Dakota has said he does not support the effort because “we’re now guessing” about the roles of individual soldiers.

The Associated Press contributed to this report.