Prosecutors in Georgia told 16 Republicans who signed on as fake electors after the 2020 presidential election that they may be subject to criminal charges as part of a sweeping investigation into former President Donald Trumps efforts to overturn Joe Biden s victory in the state.

The office of Fulton County District Attorney Fani Willis revealed the dramatic uptick in the case in court filings on Tuesday, telling the group of Trump supporters they had been designated as targets in the investigation. The 16 Republicans had gathered at the Georgia Capitol on Dec. 14, 2020, to sign an unofficial election certificate that falsely declared Trump the winner of the states presidential vote.

Biden had won Georgia and secured its 16 Electoral College votes.

Each of the sixteen persons who signed the unofficial Elector Certificate ultimately submitted to the National Archives received a similar target letter, alerting that person both that his testimony was required by the special purpose grand jury and that he was a target of the investigation, prosecutors wrote in a filing Tuesday.

The group includes several high-ranking Republicans in the state, including state Sen. Burt Jones, who is running for lieutenant governor, and David Shafer, an ally of Trump who chairs the Georgia Republican Party .

The shift of the fake electors to become targets in the inquiry rather than solely witnesses reflects the growing scope of Willis probe. Her office has been investigating if Trump or anyone in his orbit broke state laws when he sought to reverse Bidens win, including laws around election fraud and forgery statues, the Atlanta Journal-Constitution noted . Trumps Jan. 2, 2021, call to Georgia Secretary of State Brad Raffensperger to pressure him to find 11,780 votes enough to overturn Bidens margin of victory are thought to be key to any investigation.

Willis is seeking testimony from a slate of figures as part of a special grand jury around the former presidents effort to remain in power, including lawyer Rudy Giuliani and Sen. Lindsey Graham (R-S.C.). She could also move to subpoena Trump himself.

The New York Times added that the Atlanta inquiry represents some of the most pressing legal perils to Trump and his allies, even as the House select committee hearings into the Jan. 6 attack on the U.S. Capitol continue.

Lawyers for 11 of the Republicans have derided the inquiry , accusing Willis of misusing the grand jury process to harass, embarrass, and attempt to intimidate the nominee electors, not to investigate their conduct. Most of the false electors were set to testify before the grand jury next week, but the attorneys said the subpoenas were unreasonable and oppressive and many of their clients would invoke their Fifth Amendment right against self-incrimination.

The Republicans have argued that they were acting lawfully, saying their elector votes were contingent on if a court did deem them legitimate electors and Trump the winner of the state. They also say they had no knowledge of a broader national effort by Trump and his allies to pressure then-Vice President Mike Pence to block the certification of the electoral votes on Jan. 6, 2021.

Pence rejected those efforts.