Sen. Kamala Harris, D-Calif., and two House Democrats are urging Congress to pass legislation requiring carbon monoxide detectors in public housing, after an NBC News investigation found that millions of low-income Americans may be at risk from the dangers posed by the deadly gas.

Harris, a presidential candidate, along with Rep. Jesús “Chuy” García, D-Ill., and Rep. Joe Cunningham, D-S.C., sent a letter to congressional leaders Monday urging them to act swiftly to protect "the most vulnerable among us, the elderly and children living in federally-assisted public housing."

The letter followed NBC News' report last week that a Michigan couple had died of carbon monoxide poisoning in their Section 8 home. At least 13 residents of homes overseen by the Department of Housing and Urban Development have died from exposure to the colorless, odorless gas since 2003, by NBC News' count, based on news reports confirmed with authorities.

“These senseless deaths in federally-assisted housing are unconscionable,” Harris, García and Cunningham wrote in the letter.

The politicians introduced legislation in March that would require carbon monoxide detectors in federally subsidized housing across the country, including $10 million in funding to help offset the cost of installing and maintaining the devices. The bill, which has 25 cosponsors in the House, followed the NBC News investigation on the threat posed by carbon monoxide poisoning in public housing.

But neither the House nor the Senate has moved forward with the proposal, prompting the bill’s cosponsors to send their letter on Monday to the Democratic and Republican leaders of the House Financial Services Committee and the Senate Banking Committee.

Harris, García and Cunningham urged the committee leaders to “expedite consideration and passage” of the legislation.

Rep. Maxine Waters, D-Calif., chair of the House Financial Services Committee, and Sen. Mike Crapo, R-Idaho, chair of the Senate Banking Committee, did not immediately respond to requests for comment.

In mid-April, HUD announced that it would propose a regulation that would require carbon monoxide detectors in federally assisted housing. But it has not released a proposal yet — the first step in the lengthy process of creating a new federal rule.

“This is an urgent crisis," Harris said in a statement. “People are dying, and this administration still hasn’t implemented a plan to install carbon monoxide detectors in public housing units so that we can avoid any more preventable tragedies."