House Speaker Nancy Pelosi (D-Calif.) announced Thursday that the House will form a select committee to investigate the Jan. 6 attack on the Capitol by a pro-Trump mob, one month after Senate Republicans blocked an effort to form an independent, bipartisan commission.

“This morning, with great solemnity and sadness, I’m announcing that the House will be establishing a select committee on the Jan. 6 insurrection,” Pelosi said at a morning news conference, describing the day of the attack as “one of the darkest days in our nation’s history.”

“It is imperative that we establish the truth of that day and ensure that an attack of that kind cannot happen and that we root out the causes of it all,” she added.

The panel will investigate the facts and causes of the insurrection and will provide recommendations to help prevent similar attacks in the future, according to Pelosi.

Senate Republicans last month blocked the creation of an independent Jan. 6 commission, despite 35 House Republicans having endorsed the effort. That commission would have been modeled after a panel formed in the aftermath of the 9/11 terrorist attacks and charged with producing an objective account of what fueled the day’s violence.

About 10,000 people gathered at the Capitol on Jan. 6, and nearly 800 of them broke into the Capitol building.

The events of the day resulted in five deaths, and nearly 140 officers were assaulted during the attack, as they faced rioters armed with ax handles, bats, metal batons, wooden poles, hockey sticks and other weapons, authorities said.

On Wednesday, a 49-year-old Indiana woman became the first person sentenced in the Jan. 6 riot. Anna Morgan-Lloyd pleaded guilty to a misdemeanor count of demonstrating inside the Capitol; she was sentenced to three years of probation and must perform 40 hours of community service and pay $500 in restitution.

In recent weeks, a smattering of House and Senate panels have been looking into the events of Jan. 6, holding public hearings with law enforcement and military officials and, in one case, even publishing a comprehensive report examining why authorities were unable to control the pro-Trump crowd.

The select committee — which will require a majority vote in the Democratic-led House to be formed — is a signal that Pelosi wants to centralize those investigations in one body that will be equipped with subpoena power and tasked with publishing its findings.

But a select committee is all but guaranteed to be a more partisan forum than an independent commission would have been — meaning the parties may come no closer to a consensus about why Jan. 6 happened and who is to blame for it at the end of the probe than they are at present.

It is not yet clear how large Pelosi’s planned Jan. 6 panel will be or how the seats on it will be distributed. It is also not clear when she will demand the panel publish its findings. Pelosi said Thursday that the timeline “will be as long as it takes for them — the time they need to do the investigation of the causes of this.”

“There are two actual paths,” the speaker added. “One is about the root causes of it — the white supremacy, the antisemitism, the Islamophobia, all the rest of it that was so evident. . . . The other is the security of the Capitol and what it means to be ready for such an insurrection.”

She said that while authorities “could have been better prepared” for that day’s events, “I don’t think anybody would have foreseen an insurrection incited by the president of the United States.”

Republican lawmakers who voted against the creation of an independent commission openly worried that its product might negatively affect the GOP in the 2022 midterm election cycle. But the commission would have had a deadline of the end of this year to produce a report; it is far from certain that a select committee would have to function on as tight a timeline.

It is also unclear how many witnesses a select committee will be able to depose as part of its investigation.

Previously, House Democrats had hoped that an independent commission would be able to compel testimony from people who were in the highest ranks of government on Jan. 6, including President Donald Trump and the top advisers who were with him that day. But it is unlikely those individuals will respond to a subpoena issued by Democrats without a lengthy court fight.

Asked Thursday whether Democrats might seek to compel House Minority Leader Kevin McCarthy (R-Calif.) to testify about his conversation with Trump on the day of the insurrection, Pelosi declined to say.

“I’m not going into what the committee will do; that’s up to the committee to make their determination,” she told reporters. “But it is clear that the Republicans are afraid of the truth.”

If he testifies, McCarthy is likely to be asked about his Jan. 6 phone call with Trump — a conversation he has described to others as distressing. A shaken McCarthy reportedly asked Trump to help calm his supporters who had broken into the Capitol that afternoon, with some of them threatening to hang Vice President Mike Pence and physically harm Pelosi.

Trump seemed uninterested, according to a statement from Rep. Jaime Herrera Beutler (R-Wash.), who talked to McCarthy about the call.

As president, Trump managed to repeatedly stymie Democrats’ plans to seize documents from his administration and interview his aides. Now, as an ex-president, he no longer has the power to claim executive privilege over testimony, but he is unlikely to be suddenly cowed into adopting a less-litigious stance to accommodate a probe into the Jan. 6 attack.

The Democratic-led House impeached Trump for allegedly inciting the Jan. 6 riot. While 57 senators — including seven Republicans — ultimately voted that he was guilty of those charges, the body fell short of the 67 votes it would have taken to convict him.

In 2012, a GOP-led House established a select committee to look into the ambush that led to the deaths of four Americans at U.S. outposts in Benghazi, Libya. But the investigation soon descended into a tool to lob attacks at Secretary of State Hillary Clinton for using a private email server to conduct official business — a story line that dogged her throughout her failed 2016 presidential bid against Trump.

During that campaign cycle, McCarthy, then the House’s second-highest-ranking Republican, bragged that the special committee had helped hamstring Clinton’s candidacy. McCarthy opposed the proposal for an independent commission on the Jan. 6 attack.

In the time since, the parties have only dug in more deeply behind partisan lines on questions regarding Trump’s guilt or even when it comes to funding improvements to Capitol security. A bill to direct $1.9 billion in new security ventures — and paying past debts to the National Guard and others who responded to the riot — is still waiting for Senate action after barely scraping by in the House, on a 213-to-212 vote last month.