The US justice department on Thursday is reported to have issued subpoenas in response to a report that the Alaska Democrat Mary Peltola’s campaign collaborated with party operatives to get a challenger with the same name as the Republican senator Dan Sullivan on the midterm ballot.

ABC News reported the subpoenas, citing sources familiar with the matter. The federal investigation comes a day after the New York Times found that the effort to recruit a second candidate named Dan Sullivan in the Senate race set to be decided on Tuesday was led by Peltola’s campaign, which had for months denied involvement.

Earlier on Thursday, Alaska’s Republican governor, Mike Dunleavy, announced a criminal inquiry into the effort, which the Times reports was intended to confuse Alaskans who wanted to support the Republican incumbent.

Last week, Trump said he had ordered the justice department to file a lawsuit to block the certification of the Senate election if Sullivan does not win. That suit is pending.