CNN  — 

Two Republican Senate committee chairmen requested Hunter Biden’s travel information from when his father, Joe Biden, was vice president from the Secret Service director on Wednesday following the Senate’s vote to acquit in the impeachment trial of President Donald Trump.

Finance Chairman Chuck Grassley, of Iowa, and Homeland Security and Governmental Affairs Chairman Ron Johnson, of Wisconsin, announced in a letter to Secret Service Director James Murray that their panels “are reviewing potential conflicts of interest posed by the business activities of Hunter Biden and his associates during the Obama administration.”

The chairmen’s timing is notable, as the impeachment trial centered largely on Trump’s attempts to pressure Ukraine to investigate Hunter Biden and Joe Biden, his potential political rival. Trump has repeatedly made unfounded and false claims to allege that the Bidens acted improperly in Ukraine.

“We write to request information about whether Hunter Biden used government-sponsored travel to help conduct private business, to include his work for Rosemont Seneca and related entities in China and Ukraine,” the chairmen wrote, referencing a firm co-founded by Hunter Biden.

CNN has reached out to the Secret Service for comment. A spokesperson for Joe Biden’s presidential campaign declined to comment.

The chairmen asked Murray to provide a list of dates and travel locations for which Hunter Biden received a protective detail, information on whether he was on government aircraft or accompanied by family members and a description of the protective detail.

They requested the information by February 19 “to help the committees better understand Hunter Biden’s travel arrangements to conduct business related to his dealings in Ukraine and China, among other countries,” according to the letter.

Grassley and Johnson specifically cited Hunter Biden’s position on the board of directors of Burisma Holdings, a Ukrainian natural gas company, writing that it “is unclear whether Hunter Biden received government sponsored travel or a protective detail for these endeavors.” The New York Times has reported that Hunter Biden made approximately $50,000 a month in that role.

The letter also specifically points to a particular trip that both Bidens made to China in 2013.

According to The New York Times, Hunter Biden has a 10% interest in BHR Partners, a private-equity fund that the Chinese government-owned Bank of China has invested in. In December 2013, the same month the fund was officially established, Hunter Biden joined his father and one of his daughters on a trip to China. There, he met with Jonathan Li, the fund’s China-based partner. The New Yorker reported that Li met Hunter Biden at his hotel and shook hands with the vice president. Days after the start of the trip, Hunter Biden had officially joined BHR’s board, The Washington Post reported, raising questions about whether he had used his father’s access for his own personal benefit.

However, according to The New Yorker, Hunter Biden maintains that visit with Li was social, not business-related. As of May 2019, both The New York Times and The Washington Post reported that Hunter Biden had not received any money from the fund or in connection with his role as an unpaid advisory board member. In July 2019, more than two years after his father had left office, Hunter Biden purchased an equity stake in the BHR fund, valued around $430,000, according to The Washington Post.

CNN’s Tara Subramaniam, Daniel Dale and Holmes Lybrand contributed to this report.