Transportation Secretary Elaine Chao has resigned resign as the Trump administration faces more fallout.
She is the first Cabinet member to leave in wake of President Donald Trump's response to a mob of his supporters breaching the US Capitol.
Mrs Chao said the mob attack has deeply troubled her in a way that she simply cannot set aside.
A veteran of Republican administrations and the wife of the Senate Majority Leader Mitch McConnell, Chao came into her post with a focus on reviving the nation's crumbling infrastructure.
Deputy national security adviser Matt Pottinger, who was a leading figure in the development of Trump's China policy, also resigned abruptly on Wendesday.
He was followed by senior director for European and Russian affairs at the National Security Council, Ryan Tully.
Many other lower-level administration officials have announced they will resign, including several White House aides.