WASHINGTON — The Justice Department is seeking details about the formation and operation of Donald Trump's post-presidential political operation, according to three people familiar with the probe, sending a raft of subpoenas in a significant expansion of the criminal investigation of the Jan. 6, 2021, attack on the Capitol and efforts to overturn the results of the 2020 election.

A federal grand jury sent subpoenas on Wednesday to a wide range of former campaign and White House staffers asking for information about the Save America PAC, according to the people, who spoke on the condition of anonymity to discuss an ongoing probe. They described the subpoenas as broad, seeking all documents and communications about opening the PAC and every dollar raised and spent.

At least one of the subpoenas also demanded information about the plan to submit slates of phony electors claiming Trump won pivotal states, including all communications with several key lawyers and advisers involved in the effort, one of the people said. They include Rudy Giuliani, Boris Epshteyn, Bruce Marks, Victoria Toensing and Joseph DiGenova, this person said.

Another one of the three people, who has direct knowledge of one of the subpoenas, said the document was "wide ranging" and included multiple other categories of information, but this person declined to describe them. FBI agents served at least some of the subpoenas in person on Wednesday, one of the people with knowledge said.

Spokesmen for Trump and the Justice Department did not immediately respond to a request for comment. Some of the details of the subpoenas were reported by ABC and the New York Times.

Epshteyn declined to comment. So did Toensing, who is married to DiGenova. Giuliani did not immediately respond to requests for comment.

Marks said he was out of the country and wasn't aware of a subpoena. He defended the effort to submit alternate electors but distanced himself from the pressure campaign on former vice president Mike Pence to unilaterally reject some states' votes for Biden.

"I thought the vice president did the right thing," Marks said. "We're not all crazy in MAGA world."

Trump's post-presidential fundraising has already been a source of suspicion for investigators with the House Jan. 6 committee, as well as griping from some Republicans who want Trump to dip into his reserves to boost the party's Senate campaigns amid signs their candidates are behind in polls and fundraising.

This week's subpoenas were also the latest sign that the Justice Department has intensified its own parallel probe into Jan. 6. Prosecutors already charged hundreds of people involved in the Capitol riot with low-level offenses such as trespassing and attacking police, as well as accusing leaders of the violent extremist groups the Proud Boys and Oath Keepers of coordinating the attack. More recently, prosecutors began examining planning for the rally before the riot and Republican efforts to send Trump slates to the electoral college.

As part of the probe, prosecutors have sought phone records and other information from Trump's inner circle and questioned close advisers to Pence before a federal grand jury. The Washington Post reported in July that the investigation included Trump's possible role in the phony elector efforts and his pressure of federal and state officials to challenge the election results.

Some of those activities are also under scrutiny from Fulton County District Attorney Fani T. Willis (D), an elected prosecutor in the Atlanta area. Willis has said she expects a special-purpose grand jury there to deliver a report including charging recommendations by the end of the year.

The Justice Department and House panel investigations are separate from the criminal probe into handling of government secrets after Trump left office, which led to a search warrant at his Florida resort in August. On Thursday, the Justice Department appealed a federal judge's decision to appoint a special master to screen the documents seized in the search.

The government soon faces the 60-day period before an election when the Justice Department customarily avoids taking investigative steps that could be perceived as influencing voters.

The House committee investigating Jan. 6 has also shown interest in the finances of Trump's PAC, alleging that the group used false and inflammatory claims about the election to solicit donations, and asking whether parties involved had reason to believe violence could result or were motivated to continue their appeals because the millions raised. At a June hearing, a committee investigator said the Trump campaign raised hundreds of millions by sending as many as 25 emails a day asking for donations to an "Official Election Defense Fund" that did not actually exist. The panel has focused on whether federal wire fraud laws could have been violated if people sought money using claims they knew were false, The Post has reported.

Trump has raised more than $100 million for the PAC with thousands of appeals to his supporters, many of them containing misleading or false statements about the election. He has largely hoarded the money, giving limited amounts to other candidates he supports and paying some of his staff and lawyers.

The Washington Post's Devlin Barrett and Spencer S. Hsu contributed to this report.