Federal prosecutors in Alaska are investigating how Daniel J. Sullivan Jr., a retired teacher with the same name as Republican Sen. Dan Sullivan, ended up on the state's U.S. Senate ballot, with grand jury subpoenas expected as investigators examine whether the effort violated voters' rights, according to Fox News.

Fox News correspondent Bill Melugin relayed reporting from colleague David Spunt on Wednesday that the criminal investigation has been underway for months but has gained urgency following a New York Times investigation into efforts by Democrat operatives to recruit the senator's namesake. The U.S. Attorney's Office in Alaska is handling the inquiry, and investigators were preparing to seek the preservation of communications held by phone companies while preparing subpoenas for the coming hours and days.

Prosecutors are working to establish the sequence of events that led Sullivan to enter the race and are examining possible offenses involving the deprivation of Alaska voters' rights, according to the report. The investigation is expected to continue beyond Election Day. The inquiry is separate from the political controversy surrounding the candidate and does not mean that any individual has been charged with a crime.

The federal investigation predates the latest revelations. ABC News previously reported that authorities were examining possible wire fraud or a conspiracy related to the fairness of the election process. At that stage, it remained unclear who, if anyone, could ultimately face charges.

The controversy intensified after The New York Times reported on a months-long effort involving individuals associated with Democrat Senate nominee Mary Peltola's campaign and the Democratic Senatorial Campaign Committee to recruit additional candidates. According to the newspaper's investigation, the effort included searching for Alaska residents who shared the incumbent Republican senator's name.

The Times based its reporting on interviews with 12 sources, text messages and documents. The account raised questions about whether the recruitment effort was intended to confuse voters by placing a second Dan Sullivan on the ballot against the sitting senator.

Elisa Rios, Peltola's former campaign manager, told The Times that voters should know about the recruitment effort. Her account became part of the growing scrutiny surrounding the campaign, although the reporting has not established that Peltola personally directed the recruitment operation.

Peltola's campaign denied involvement in either Sullivan's candidacy after the report appeared.

"The Alaskans for Mary campaign has no involvement with either Sullivan campaign," the campaign said in a statement reported by Alaska Public Media. "Like Mary, our campaign is focused on lowering costs and fixing the rigged system in DC."

The Democratic Senatorial Campaign Committee has also denied participating in the recruitment effort. Daniel J. Sullivan Jr. has maintained that his candidacy was independent of Peltola's campaign.

The dispute over Sullivan's eligibility began well before the latest reports. Alaska election officials initially sought to exclude him from the ballot, concluding that his filing was intended to mislead voters. Sullivan challenged the decision in court, and the Alaska Supreme Court ultimately upheld his eligibility to run.

President Donald Trump has also weighed in, calling for legal consequences for Peltola and the second Sullivan. Trump accused Democrats of recruiting a candidate with the same name as the incumbent senator to confuse voters and divert support from the Republican.

"This is Voter Fraud at the Highest Level, and the Dumocrat Candidate, who was involved in the scheme, Mary Peltola, should be removed from the Ballot and prosecuted — So should the FAKE Dan Sullivan. Nothing else will do! This behavior in our Elections cannot be allowed to continue," Trump wrote.

Trump's accusations go beyond what has been publicly established by the investigation. Federal prosecutors are examining whether laws were violated, but the investigation has not itself established criminal wrongdoing by Peltola, her campaign or the DSCC.

The inquiry now adds a federal criminal investigation to an election dispute that has already involved state election officials, court challenges and competing accounts from the campaigns. Investigators are expected to continue examining communications and the circumstances surrounding Sullivan's candidacy after Election Day, as they determine whether the recruitment effort violated federal law or the rights of Alaska voters.