WASHINGTON — Rep. Katherine Clark, D-Mass., became the highest-ranking House Democrat to call for opening an impeachment inquiry into President Donald Trump.

"I deeply respect the committee work of House Democrats to hold the president accountable, including hearings, subpoenas and lawsuits. All of our efforts to put the facts before the American people, however, have been met with unprecedented stonewalling and obstruction," the sixth-ranking House Democrat said in a statement Thursday evening, adding, "That is why I believe we need to open an impeachment inquiry that will provide us a more formal way to fully uncover the facts."

Clark made her announcement the day after former special counsel Robert Mueller testified before two House committees about his investigation into Russia's interference in the 2016 election, possible coordination with the Trump campaign and subsequent efforts by the president to obstruct the probe.

"Since the release of the Mueller report in April, it has been clear that the president committed impeachable offenses by welcoming interference from a hostile foreign power in the 2016 election and then attempting to obstruct the investigation into his unpatriotic actions," Clark said. "Moreover, he said he would do it all again if given the chance."

Four other House Democrats also publicly called for moving ahead with impeachment since Mueller's testimony — Reps. Andre Carson of Indiana, Lori Trahan of Massachusetts, Peter DeFazio of Oregon and Lisa Blunt Rochester of Delaware — which brings the number to 94 Democrats who are backing an impeachment inquiry, according to an NBC News count.

There has been an active discussion for several months inside the House Democratic caucus about whether a formal impeachment inquiry should be launched.

On Wednesday night, following Mueller's testimony before the House Judiciary and Intelligence committees, House Democrats met behind closed-doors where they discussed ways that impeachment could move forward.

Speaker Nancy Pelosi advocated for continuing House investigations into the president to gather facts and pursue litigation to make the strongest case possible if lawmakers decide to impeach. She said, more clearly than she has previously, that each member can decide on impeachment based on their conscience and constituents.

Clark said in her statement that "an impeachment inquiry is a process, not an outcome, but I fear there is no amount of wrongdoing that we could uncover that would convince Senate Republicans to hold the President accountable."