The conservative social network Parler informed the FBI of “specific threats of violence being planned at the Capitol” in advance of the Jan. 6 riot there, the company asserted in a letter to lawmakers Thursday, deepening questions about why the bureau did not muster a more aggressive response.

In a lengthy letter to Rep. Carolyn B. Maloney (D-N.Y.), chair of the House Committee on Oversight and Reform, lawyers for Parler wrote that the company referred violent content from its platform to the FBI more than 50 times, and those referrals included specific threats to the U.S. Capitol.

On Dec. 24, for example, Parler turned over to the bureau a post from a user who “called for the congregation of an armed force of 150,000 on the Virginia side of the Potomac River to ‘react to the congressional events of January 6th,’ ” lawyers for the company wrote, an apparent reference to lawmakers’ formal count of the election results. And on Jan. 2, the lawyers wrote, Parler gave the bureau posts by a user who claimed he would be wearing body armor at a planned event on Jan. 6 and asserted it was “not a rally and it’s no longer a protest.”

“This is the final stand where we are drawing the red line at Capitol Hill,” the user wrote, according to the letter. “I trust the American people will take back the USA with force and many are ready to die to take back #USA so remember this is not a party until they announce #Trump2020 a winner . . . And don’t be surprised if we take the #capitalbuilding . . .”

In the same referral, Parler included the post of another user who asserted that President Donald Trump, whose provocative address to thousands of supporters leading up the riot led to his impeachment, needed the group to “cause chaos” so he could invoke the Insurrection Act, wrote the lawyers, Michael S. Dry and Ephraim “Fry” Wernick of the firm Vinson & Elkins.

Parler, which was launched by an investment from billionaire Republican megadonor Rebekah Mercer, is a social networking site that pitches itself as a free-speech alternative to tech giants like Twitter and Facebook.

The FBI declined to comment.

The bureau and other federal law enforcement agencies, such as Capitol Police, have faced criticism for not reacting more aggressively to intelligence that seemed to indicate the possibility of violence on Jan. 6. The matter is being investigated by the inspectors general for several federal agencies.

A Capitol police intelligence report prepared three days before the riot warned of a violent scenario in which “Congress itself” could be the target of angry Trump supporters. The day before, the FBI’s Norfolk field office prepared a document explicitly warning that extremists were preparing to travel to Washington to commit violence and “war.”

Officials have said that in the weeks leading up to the rally, the bureau was mindful of online chatter suggesting possible violence, and agents even visited some far-right extremists, hoping to learn more about their plans and dissuade them from coming to D.C.

The Jan. 5 warning from the Norfolk office was shared with the field office in Washington, and within an hour, officials in a command post there were briefed, FBI Assistant Director in Charge Steven M. D’Antuono has said. The document was also shared through a Joint Terrorism Task Force that includes representatives from the Capitol Police and other law enforcement agencies, D’Antuono has said.

But D’Antuono also said in the days after the riot that the FBI did not have information in advance of anything other than a rally that was planned for Jan. 6. FBI officials have since said it can be challenging to distinguish aspirational boasts from actual threats in the massive amount of incendiary chatter online, though FBI Director Christopher A. Wray has conceded that what happened at the Capitol was not “an acceptable result.”

In the wake of the riot, Amazon suspended Parler from its web-hosting service, knocking the social network offline for more than a month on the assertion that it had violated terms of service by not adequately moderating content. Amazon founder Jeff Bezos owns The Washington Post.

Parler’s lawyers asserted in their letter that the treatment was “unlawful and anticompetitive,” and that a Forbes analysis of court documents for those charged in connection with the riot found they more frequently reference other social networks, such as Facebook, YouTube and Instagram. Separately on Thursday, the House Energy and Commerce Committee grilled the chief executive officers of Google, Facebook and Twitter on the role their companies played in promoting extremism.

“Far from being the far-right instigator and rogue company that Big Tech has portrayed Parler to be, the facts conclusively demonstrate that Parler has been a responsible and law-abiding company focused on ensuring that only free and lawful speech exists on its platform,” the lawyers wrote, adding that Parler had “developed a strong working relationship with the FBI to facilitate cooperation and proactive reporting of unlawful incitement and violent threats.”

The lawyers wrote that Parler also flagged to the FBI in December violent rhetoric from a user who threatened to kill politicians, including then-Attorney General William P. Barr, and in January forwarded a post that included a picture of Hillary Clinton behind a noose. Attached to the letter were redacted screenshots of Parler’s correspondence with the FBI, which appeared to show an agent reaching out to establish a relationship and later expressing gratitude for the company’s help.

“Even after the violent attacks stopped, Parler continued to dutifully and proactively report posts to the FBI where users threatened additional violence,” the lawyers wrote.