WASHINGTON >> The Department of Homeland Security will undergo an internal review to root out white supremacy and extremism in its ranks as part of a larger effort to combat extremist ideology in the federal government, officials said today.

The task of identifying extremists throughout the United States, and specifically in government agencies, has come to the top of President Joe Biden’s agenda since Jan. 6, when a pro-Trump mob stormed the U.S. Capitol. Many of the rioters were found to be members of extremist groups.

“We recognize that domestic violent extremism and the ideology, the extremist ideologies that spew it, are prevalent,” said Alejandro Mayorkas, the homeland security secretary. “We have a responsibility, given what we do, to ensure that that pernicious influence does not exist in our department.”

The review comes shortly after the Pentagon completed a 60-day “stand down” to address extremism after a number of veterans were found to have taken part in the Capitol riot. The Biden administration is assessing whether other agencies will have similar inquiries as part of a broader review started this year to assess how the federal government combats domestic extremist threats.

The announcement today highlights the administration’s decision to prioritize combating domestic extremism after decades in which the government at times dismissed it as a minor threat or hesitated to invest additional resources to fight it. It is also a pivot from the approach taken by President Donald Trump, who pressured federal agencies to divert resources to target the antifa movement and left-wing groups, even though law enforcement authorities concluded that far-right and militia violence was a more serious threat.

The homeland security review calls for a team of senior officials to determine whether extremist ideology is prevalent in its various agencies, including the Border Patrol, Immigration and Customs Enforcement, the Secret Service and the Coast Guard. The department works to prevent domestic terrorism threats, as well as conduct immigration enforcement, protect the president and respond to national emergencies.

Rooting out extremism across the government is enormously challenging; the military alone has 1.3 million active-duty troops. Homeland security is one of the largest law enforcement departments in the country, with more than 240,000 employees.

Gil Kerlikowske, who was a Customs and Border Protection commissioner under President Barack Obama, said that the internal review would be complicated given that many agents communicate on private social media pages or in chat rooms.

“This is pretty tricky,” he said. “On every level.”

As part of the review, senior officials will establish an internal process for agents who are found to be associated with extremist groups or who espouse those beliefs online or while on duty, Mayorkas said.

He said he was “mindful of the constitutional right to free speech.”

“There is a marked difference between that right and violence in furtherance of extremist ideologies,” Mayorkas said.

Biden has made fighting domestic extremism an early priority.

Shortly after taking office, he ordered the director of national intelligence to work with the FBI and Homeland Security Department on a comprehensive assessment of how the government combats extremism. The administration followed up with an intelligence report delivered to Congress last month that identified white supremacists and militia groups as top national security threats.

In a memo to all department employees today, Mayorkas called domestic extremists “the most lethal and persistent terrorism-related threat to our country today.”

The department will also issue guidance to employees in the coming days for reporting “insider threats and other actions associated with domestic violent extremists,” according to the memo. Biden this month released a spending proposal that included an additional $84 million for Customs and Border Protection and ICE to improve investigations of workforce complaints, “including those related to white supremacy or ideological and nonideological beliefs.”

Mayorkas declined to say in an interview how many active members of his department had been identified as taking part in the Capitol riot, citing continuing investigations.

Department employees have a right to share their views on immigration policy, Mayorkas said, and if an individual “in a back office communicates anti-immigrant sentiment, that is one thing that may or may not warrant a supervisorial address.”

But if an ICE agent said such a statement while conducting enforcement, that “could impair the integrity of the work of the department” and warrant a different punishment, Mayorkas said.

Kerlikowske said the review could result in a backlash in the agency.

“I think there’s real potential for that,” he said, “if you’re telling them what they can post and what they can’t post.”