The House Intelligence Committee has started asking federal agencies about the Obama administration's approval of a Russian acquisition of a large uranium mine—a deal that is now under new scrutiny amid revelations about a sweeping Russian bribery scheme from an FBI informant.

The panel so far is only making "preliminary inquiries" and has not launched a formal, full-scale investigation, according to a knowledgeable GOP source.

Information from the FBI informant and court documents about a criminal investigation and prosecution of Russian officials for bribery—and whether key U.S. government agencies knew about the probe—are raising new questions about the uranium deal and whether the United States should have approved it.

New details about the extensive Russian bribery scheme and the U.S. government's prosecution of it, reported by the Hill newspaper and Circa News, also has drawn renewed attention to millions of dollars the Clintons received from Russians with ties to the state-owned entity involved in the acquisition.

The House Intelligence panel's questions follow public statements this week from Sen. Chuck Grassley (R., Iowa), the chairman of the Senate Judiciary Committee, who said on Wednesday he started investigating the new information about the uranium deal last week and pressed Attorney General Jeff Sessions about it during a committee hearing Wednesday.

Sessions would not say whether the Justice Department had launched an official investigation into the matter but told Grassley that his concerns about the deal "would be reviewed."

Grassley during the Wednesday hearing said the Clinton Foundation had received millions of dollars from "interested parties" in the uranium deal and highlighted a $500,000 payment former President Bill Clinton received for a speech in Moscow before a Russian-government-aligned bank.

Grassley on Thursday called on the Justice Department to lift a gag order on an FBI informant barring him from speaking to Congress about the Russian bribery scheme and any links to the Obama administration's decision to approve the Moscow takeover of a U.S. uranium mine.

The Justice Department during the Obama administration reportedly threatened to prosecute the informant if he disclosed details of his involvement in the investigation to Congress.

Grassley said he said he also questioned the circumstances surrounding the uranium deal in 2015.

Sen. John Barrasso (R., Wyo.) asked the Justice Department this week for documents related to the FBI's investigation into the uranium deal, as the Washington Free Beacon reported Thursday.

Barrasso's concerns about the deal first began in 2010, when he learned that Rosatom, Russia's state-owned nuclear arm, would be acquiring up to 20 percent of U.S. uranium, in a deal with Canada-based Uranium One.

The senator, a senior member of the GOP leadership who sits on the Energy and Natural Resources Committee, says the Obama administration never responded to his requests for information after reports that Bill Clinton had received the $500,000 sum for speaking to a Moscow state-aligned bank and several Uranium One officials donated $2.35 million to the Clinton Foundation.

Key House Republicans provided some of the harshest public warnings about the deal in 2010 before it was approved.

Four top House Republicans raised the alarm about the Uranium One deal with Russia, citing "widespread and continuing" Russian corruption and urging a top Obama official to block it.

The lawmakers sent a letter to then-Treasury Secretary Timothy Geithner in October 2010 urging him not to approve the sale of the U.S uranium mine to a subsidiary of Rosatam, Russia's state-owned energy firm that serves as its main nuclear agency. They released the letter in a press release Oct. 5, 2010. The U.S. government moved forward and approved the deal later that month.

The GOP lawmakers who signed the letter are: Reps. Ileana Ros-Lehtinen of Florida and Peter King of New York, along with then-Reps. Spencer Bachus of Alabama and Howard "Buck" McKeon of California. The lawmakers at the time served, respectively, as the ranking members of the House Foreign Affairs, Homeland Security, Financial Services and Armed Services Committees.

"Rosatom is a state-owned entity, overseen by a government that has shown little if any inclination to effectively address the widespread and continuing corruption within Russia, particularly its energy sector," the lawmakers wrote at the time.

The Republicans said the deal also raises serious questions because "Russia has a record of transferring dangerous materials and technologies to rogue regimes, such as those in Iran and Syria."

"Its willingness to provide nuclear assistance to any regime with cash and its repeated attempts to undermine U.S. nonproliferation efforts disqualifies Russia from being regarded as a reliable partner," they wrote.

As treasury secretary, Geithner served on the Committee on Foreign Investment in the United States (CFIUS), the federal interagency that considers the national security implications of foreign investments. He served alongside some of the most powerful members of President Obama's cabinet, including Secretary of State Hillary Clinton, Attorney General Eric Holder, and Defense Secretary Robert Gates.

Members of Congress now want to know if CFIUS and other U.S. agencies that signed off on the transaction were aware of the FBI's criminal probe into the Russian bribery scheme. As attorney general, Holder would have known about the FBI probe.

In addition to the Russian corruption issues, the GOP lawmakers warned that Rosatom also had a history of training Iranian scientists and designed and built Iran's Bushehr nuclear power plant, which they said had just become operational a few months prior, in August, 2010.

Russia, they asserted, was already supplying that nuclear plant with enriched-uranium fuel rods, and has signaled its interest in building further nuclear reactors in Iran.

"This cooperation has caused great distress that it could advance Iran's nuclear ambitions, be it through the extraction of weapons-grade plutonium from the reactor or the use of Bushehr (and any future additional reactors) as a cover for the prohibited transfer of other sensitive technology," they wrote. "It has also undermined longstanding efforts to compel Iran to abandon its pursuit of nuclear weapons."

Officials for Uranium One USA, the entity that owned the U.S. uranium mine, said before the deal went through that they were skeptical the transaction would result in the transfer of any mined uranium to Iran.

The lawmakers pushed back on that idea, arguing that they "remain convinced" that Iran could receive uranium supplies through direct or secondary proliferation.

Just a few years earlier, in 2007, Rosatom had signed an agreement to help build nuclear facilities in Burma and train Burmese scientists, despite U.S. concerns about the Burmese government.