The passing of House Oversight Committee Chairman Elijah Cummings leaves a vacancy in the leadership of the congressional impeachment inquiry, as the powerful Democrat was spearheading the efforts alongside Adam Schiff and Eliot Engel.

Cummings, of Maryland, passed away early Thursday “due to complications concerning longstanding health challenges,” his office said in a statement. The late congressman had been in poor health over the past few years, navigating the Capitol in a motorized cart and with a walker.

Rep. Carolyn Maloney, D-N.Y., the next in seniority to take over the gavel of the committee, is now filling Cummings' post and will serve the "acting" Oversight Committee chair.

Cummings was tasked with the House impeachment inquiry into President Trump last month, when House Speaker Nancy Pelosi, D-Calif., announced the formal process following revelations surrounding the president’s phone call with the Ukrainian president over the summer.

Cummings, along with House Intelligence Committee Chairman Adam Schiff, D-Calif., and House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y., was leading the inquiry—sending subpoenas, document requests, and conducting interviews with Trump administration officials who could hold information pertinent to the effort.

Each official House impeachment inquiry statement or update was issued on behalf of all three committee chairs, despite the fact that Cummings had not been seen on Capitol Hill in the last several weeks during some of those prominent closed-door interviews with officials.

"Elijah Cummings was the heart and soul of our caucus, a dignified leader with a voice that could move mountains. He was our moral and ethical North Star," Schiff tweeted Thursday. "Now we will be guided by his powerful memory and incomparable legacy. Rest In Peace, my friend."

Meanwhile, as news spread of Cummings’ passing on Thursday, the Oversight Committee postponed a planned hearing, and House Republicans canceled a press conference where they planned to lambast Democrats over the impeachment inquiry and said it would be rescheduled.

“We are deeply saddened by the passing of Elijah Cummings, a man of great consequence and significance on the Oversight Committee for the last twenty years,” Committee Ranking Member Jim Jordan, R-Ohio, said in a statement Thursday. "He injected an unyielding passion and purpose into his work on the Committee.”

Jordan added that his prayers were with the Cummings family and his staff.

“Their loyalty and affinity for him speaks volumes about his character,” Jordan said.

During a press conference Thursday, Pelosi, when asked about the timeline going forward on the impeachment inquiry, said: "The timeline will depend on the truth line."

She also was asked if the Democrats would consider what American voters wanted in terms of the president's removal.

"The voters are not going to decide whether we honor our oath of office," she said.

Meanwhile, President Trump, who was the subject of not only the impeachment inquiry but other investigations led by Cummings and his committee, sent his condolences to the Cummings family and friends.

“I got to see first hand the strength, passion, and wisdom of this highly respected political leader,” Trump tweeted Thursday morning. “His work and voice on so many fronts will be very hard, if not impossible, to replace!”

He clashed with Trump after the president criticized his district as a "rodent-infested mess" where "no human being would want to live."

Cummings replied that government officials must stop making "hateful, incendiary comments" that only serve to divide and distract the nation from its real problems, including mass shootings and white supremacy.

"Those in the highest levels of the government must stop invoking fear, using racist language and encouraging reprehensible behavior," Cummings said in a speech in August at the National Press Club.

Fox News' Chad Pergram, Alex Pappas and The Associated Press contributed to this report.