Federal prosecutors are examining the decision by Republican electors in some states won by President Joe Biden in 2020 to send in signed statements purporting to affirm Donald Trump as the victor of the election, a top Justice Department official said Tuesday.

Their actions were criticized at the time as a political stunt meant to bolster Trump's unfounded claims of election fraud. But they have drawn additional scrutiny in recent weeks, as the House committee investigating the Jan. 6, 2021, attack on the Capitol seeks to understand the origin of the Trump elector slates, and two Democratic attorneys general, in New Mexico and Michigan, have asked federal prosecutors to investigate whether the certifications could amount to a crime.

Deputy Attorney General Lisa Monaco confirmed prosecutors' consideration of what she termed the "fraudulent elector certifications" in an interview with CNN.

"We've received those referrals. Our prosecutors are looking at those, and I can't say anything more on ongoing investigations," Monaco said.

The Trump electors' efforts were hardly a secret. The groups in Arizona, Georgia, Michigan, Nevada and Wisconsin — all states that had officially approved Biden electors — acted publicly in mid-December 2020. They said they were adopting a tactic used by Democrats in Hawaii decades ago in hopes that some later court decision might make their meaningless votes actually count. Republicans in Pennsylvania and New Mexico also sent certificates, but those documents explicitly stated that they were to be considered only if the election results were upended.

The breadth of federal prosecutors' review was not immediately clear. Nor was it clear whom they might be targeting or what crimes they might be considering. The electors were aided in their effort by Trump campaign officials and Trump attorney Rudolph Giuliani, who said publicly that the rival slates were necessary and appropriate. Former campaign officials and party leaders, speaking on the condition of anonymity to discuss private conversations, have previously said that Giuliani oversaw the effort behind the scenes.

A Justice Department spokesman declined to comment Tuesday on when prosecutors began looking into the matter, whom they were targeting or even if they were conducting a full-fledged investigation, rather than just assessing referrals from state attorneys general.

Lynsey Mukomel, a spokeswoman for Michigan Attorney General Dana Nessel, said in an e-mail on Tuesday: "Our department still has an open investigation and we will continue to cooperate with the federal authorities as we pursue parallel efforts."

Nessel had said previously that prosecutors "took the information that was provided," and her solicitor general had spoken with the acting U.S. attorney in the Western District of Michigan. She said she hoped officials would discuss the matter with those at the Justice Department in D.C. and "ensure that this is going to be taken seriously by Attorney General Merrick Garland and those who are working on any of these issues related to the 2020 election."

New Mexico Attorney General Hector Balderas said in a statement on Tuesday: "I am pleased the DOJ is looking into this matter, as these disturbing allegations require that federal authorities partner with state law enforcement agencies across the country to ensure integrity in the election process."

The Justice Department generally does not confirm the existence of investigations. But Garland and other top officials have faced pressure to do and say more about their efforts to hold accountable those who sought to subvert Biden's win — both during the Capitol riot and before it.

Some commentators and lawmakers have pressed the department to be more aggressive in examining the conduct of Trump and those close to him. As of earlier this month, FBI agents had not sought to interview or gather materials from some of Trump's most loyal lieutenants about their strategy sessions at the Willard hotel on how to overturn the results of the 2020 election; nor had the department reached out to the Georgia secretary of state's office about Trump urging its leader to "find" enough votes to reverse his defeat.

According to CNN, Monaco "did not go into detail about what else prosecutors are looking at from the partisan attempt to subvert the 2020 vote count." But, she noted: "More broadly, look, the attorney general has been very, very clear. We are going to follow the facts and the law, wherever they lead, to address conduct of any kind and at any level that is part of an assault on our democracy."