WASHINGTON (Reuters) – U.S. Supreme Court Justice Clarence Thomas attended at least two events for the conservative Koch network of donors in recent years, ProPublica reported on Friday, citing former employees and donors with the alliance.

Thomas was brought in to the private events as a fundraising draw for the donor network, which has had multiple cases before the nation’s top court, the sources told ProPublica.

Reuters could not immediately confirm the report, which follows earlier reports on the conservative justice’s ties to a wealthy benefactor that have raised larger questions about the Supreme Court justices’ ethical conduct and prompted some pushback by Democrats in Congress.

A representative for the Koch network could not immediately be reached for comment on the report but told ProPublica that Thomas was not “present for fundraising conversations.”

“The idea that attending a couple events to promote a book or give dinner remarks, as all the justices do, could somehow be undue influence just doesn’t hold water,” a network spokesperson told the nonprofit news organization.

A representative for the Supreme Court did not immediately respond to a request for comment.

ProPublica reported that Thomas attended Koch donor events at least twice over the years, including a January 2018 private dinner for network donors. The flight to the event was not disclosed on Thomas’ annual filing that year, it said.

The justice previously has faced scrutiny following revelations that he did not disclose luxury trips and transactions paid for by the wealthy Texas businessman Harlan Crow.

In August, Thomas filed his delayed financial disclosure forms for 2022 detailing private jet travel that he said was necessitated by security concerns and including items left out of prior disclosures.

The federal judiciary’s code of conduct includes a provision judges cannot participate in fundraising, but the code does not apply to the Supreme Court. Chief Justice John Roberts has said the justices consult the code in assessing their own ethical obligations.

Democrats in the U.S. Senate are pushing a bill that would mandate an ethical code for the high court, but it would need Republican support to pass the chamber and would not likely pass the Republican-controlled House of Representatives.

Roberts has said the court is weighing steps related to conduct but has not taken public action.