WASHINGTON (Reuters) - Republican lawmakers are pressing forward with an investigation into the 2010 sale of a Canadian uranium company, which owned 20 percent of U.S. uranium supplies, to a Russian government firm, despite five congressional inquiries having found no evidence of wrongdoing.

Chairman of the House Intelligence Committee Devin Nunes (R-CA) speaks during a presser in Capitol Hill, Washington, U.S., October 24, 2017. REUTERS/Carlos Barria

Copies of letters by the heads of two U.S. House of Representatives committees released on Wednesday showed they were seeking documents and other material on the deal from the FBI, the Treasury and State Departments and the Office of the Director of National Intelligence. The letters set a deadline of Nov. 30.

Devin Nunes, chairman of the House Intelligence Committee, and Trey Gowdy, chairman of the House Oversight and Government Reform Committee, opened investigations on Oct. 24 into the agreement struck during the previous administration of President Barack Obama, a Democrat.

The committees “have questions ... about the review and approval” of the sale of Uranium One - which owned 20 percent of U.S. uranium supplies - by the U.S. Committee on Foreign Investment in the United States, or CFIUS, according to the letters.

The committees also want to know if the FBI “had evidence that Russian nuclear industry officials were engaged in bribery, kickbacks, extortion and money laundering,” the letters said.

Although Hillary Clinton was not mentioned by name, the letters reflect unsubstantiated allegations by U.S. President Donald Trump, Republican lawmakers, and right-wing media that the 2016 Democratic nominee masterminded the approval of the sale in return for donations to the Clinton Foundation.

Five committees in the U.S. House and Senate found no evidence that Clinton was behind the CFIUS’ approval of the deal, according to congressional records.

In Twitter posts, Trump has called for an investigation of the sale, and Attorney General Jeff Sessions said on Tuesday he is evaluating whether to appoint a special counsel.

Democrats and other critics say the allegations are baseless, and that Trump and his supporters are fanning them to distract attention from Special Counsel Robert Mueller’s probe into whether there was any collusion between the Trump election campaign and Russia.

While Clinton was Secretary of State at the time of the sale, her department has only one of nine votes on CFIUS, which is chaired by the Treasury Department and approved the sale unanimously.

In addition, the State Department CFIUS seat was occupied not by her, but by Jose Fernandez, then-assistant secretary for economic, energy, and business affairs, who has said Clinton played no role in the decision.

The sale also was approved by the Nuclear Regulatory Commission and Obama.

In a related development, Representative Elijah Cummings, the top oversight committee Democrat, objected on Wednesday to the Republicans’ refusal to give Democrats access to an unidentified FBI informant whom Republican lawmakers say has new evidence in the case.

In a letter to Gowdy, Cummings said Republican lawmaker Ron DeSantis told Fox News on Oct. 22 that he thought the informant could link the approval of the Uranium One sale to “millions of dollars” that “sources connected to Uranium One” donated to the Clinton Foundation.