WASHINGTON — Democratic lawmakers called on the Trump administration on Thursday to review an investment in Kentucky by a Russian aluminum company that they say has raised concerns about Russian influence on the economy and national security of the United States.

The Russian aluminum company, Rusal, announced on Thursday that its board had approved a $200 million investment in a planned aluminum plant in Ashland, Ky., in partnership with Braidy Industries, a private company based there.

The announcement came less than four months after the administration lifted sanctions on Rusal and its parent company, EN+. The sanctions had banned the companies from doing business in the United States, and would have prevented the Kentucky deal, under which Rusal will own 40 percent of the plant and will supply it with unfinished aluminum for processing and sale to large institutional buyers, including automakers and airplane manufacturers.

The sanctions had been imposed last year because the companies were owned and controlled by the influential Russian oligarch Oleg V. Deripaska, a Kremlin ally who the Treasury Department accused of aiding Russia’s "malign activity” around the world.

After a sophisticated legal and lobbying campaign financed by the companies, the Treasury Department announced a deal last year to lift the sanctions in exchange for a restructuring intended to reduce Mr. Deripaska’s control and ownership of the companies. Yet a confidential, legally binding document detailing the agreement showed that Mr. Deripaska, who remains under personal sanction by the United States, and his allies would retain majority ownership of EN+. VTB, a Russian government-owned bank under limited United States sanctions, would own about 24 percent of EN+ under the deal.

A group of Democratic lawmakers with top roles on committees overseeing the Treasury Department sent a letter on Thursday to Steven Mnuchin, the Treasury secretary, saying they were "deeply alarmed" by Rusal’s investment in the Kentucky mill.

"Given that EN+ is a company substantially owned by individuals and entities with close ties to the Russian government, we believe the proposed transaction warrants immediate review by the Committee on Foreign Investment in the United States," the lawmakers wrote in the letter.

The Committee on Foreign Investment in the United States is an interagency panel led by the Treasury Department that can block foreign investments in American companies on national security grounds.

The panel rarely discloses the existence of reviews, and a spokesman for Mr. Mnuchin declined to comment on the potential Rusal investment. The companies say the deal is expected to close before the end of June, and the plant is expected to be operational by 2021.

Craig Bouchard, the chairman and chief executive of Braidy Industries, rejected the notion that the deal could be blocked by the committee, citing a provision in the regulations excluding from review start-ups or so-called greenfield investments, such as building a plant.

Rusal’s investment is only in the new mill, he said in a statement. "It is not an investment at the parent company level."

The plant could bring hundreds of "permanent green advanced manufacturing jobs to Appalachia," Mr. Bouchard said in the statement.

He dismissed criticism of Rusal’s involvement as politically driven, adding, "We take no sides in the political divisiveness plaguing our country at this time." His company began negotiations with Rusal only after the sanctions were lifted, he said, explaining that he was satisfied that the sanctions relief deal ended Mr. Deripaska’s control of the companies.

Mr. Bouchard said representatives from his company did not discuss the Rusal investment before it was announced with the Trump administration or Kentucky’s senators, Mitch McConnell and Rand Paul, both of whom are Republicans.

Mr. McConnell, the Senate majority leader, helped defeat a bipartisan effort in January to block the sanctions relief deal for Rusal. His spokesman said Mr. McConnell’s support for lifting the sanctions was unrelated to the potential investment in Kentucky, which was not publicly announced until last month — months after the vote.

Lobbying filings suggest that, just before the April announcement, David Vitter, a former Republican senator who is being paid to lobby for EN+, reached out to give Mr. McConnell "a heads-up" about the announcement.

Mr. Paul, who also voted to lift the sanctions, said in a statement that he was "excited that Braidy Industries chose Ashland, Ky., for their headquarters and will create hundreds of jobs for Kentucky workers." He added that he had "no knowledge of any kind as to their financing, but I do find it deplorable that the fake news media would try to turn a big win for Kentucky into some partisan propaganda story."

The investment comes as Rusal is pushing to expand into other parts of the United States.

Shortly after the announcement of the planned investment in Kentucky, Lord Barker of Battle, the former British member of Parliament who is the chairman of EN+, sent letters to governors of eight states saying "we see significant opportunities across the whole aluminum industry value chain in North America."

The letters — sent to the governors of Alaska, Colorado, Indiana, Michigan, Ohio, Oregon, Pennsylvania and Wisconsin — included articles about the Kentucky plan. "This investment is just the beginning of our long-term ambitions," Lord Barker wrote. "If appropriate, I would be delighted to explore these issues in more detail with you and your staff."

Representative Lloyd Doggett, Democrat of Texas, who signed the letter to Mr. Mnuchin requesting a review, said "perhaps it’s just an unusual coincidence" that Rusal is "placing in Kentucky the largest new aluminum plant built here in decades."

"We seek a thorough review of the national security implications of Rusal putting down American roots in the Blue Grass State," he added.

The letter said that "Russia remains a central threat" to the United States. "The proposed investment by EN+ — a company that is majority owned by a U.S.-sanctioned Russian national and Russian state bank — in an American aluminum mill, raises serious questions of national security."

Representatives for Mr. Deripaska did not immediately respond to a request for comment. He is suing to overturn the United States sanctions against him.