Democratic Sen. Elizabeth Warren sent letters Tuesday to federal banking regulators and Secretary of Housing and Urban Development Ben Carson, accusing them of rolling back anti-discrimination protections for people of color in the face of a wave of modern-day redlining.

“Over the past year, HUD has taken a number of steps that threaten to undermine existing fair housing laws and regulations,” she wrote, accusing the housing secretary of a “disturbing pattern of undermining and failing to enforce housing and lending laws.”

The letters were the latest salvo from the Massachusetts senator, who has taken up the issue of redlining in the wake of a February investigation from Reveal from The Center for Investigative Reporting, which found that in 61 metro areas across America, people of color were far more likely to be denied a home loan than their white counterparts, even when they made the same amount of money and wanted to take on the same size loan and buy in the same neighborhood.