Senate Finance Committee Chairman Chuck Grassley, R-Iowa, and Senate Homeland Security and Governmental Affairs Committee Chairman Ron Johnson, R-Wis., announced in a letter Wednesday they are seeking "records of Hunter Biden’s travel while he was under U.S. Secret Service protection as they continue to investigate potential conflicts of interest to boost his business ventures in Ukraine and China."

The request to U.S. Secret Service Director James Murray was revealed just minutes after the Senate voted to acquit President Trump. It underscored the continuing importance of a matter at the heart of the impeachment proceedings -- whether Hunter Biden, who obtained a lucrative role on the board of a Ukrainian company with no relevant experience while his father oversaw Ukraine policy as vice president, deserved the scrutiny Trump suggested in his July 25 call with Ukraine's new president.

"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 senators wrote, referring to the company co-founded by the younger Biden.

READ THE LETTER TO THE SECRET SERVICE

Grassley and Johnson suggested the Secret Service might have information concerning Hunter Biden's apparent sweetheart deals in those countries, especially concerning his position as one of nine directors at BHR -- a private-equity company controlled by Chinese government-backed stakeholders.

"In December of 2013, one month after Rosemont Seneca's joint venture with Bohai Capital to form BHR, Hunter Biden reportedly flew aboard Air Force Two with then-Vice President Biden to China," the senators wrote. "While in China, he helped arrange for Jonathan Li, CEO of Bohai Capital, to 'shake hands' with Vice President Biden."

"Afterward," they continued, "Hunter Biden met with Li for reportedly a 'social meeting.' After the China trip, BHR's business license was approved. Then, in 2015, BHR joined with Aviation Industry Corporation of China (AVIC) to acquire Henniges, which was the 'biggest Chinese investment into U.S. automotive manufacturing assets to date.'"

The letter continued: "In addition to business dealings in China, Hunter Biden also served as a board member for Burisma Holdings, a Ukrainian energy company. In April 2014, around the time Hunter Biden joined Burisma, Vice President Biden reportedly became the 'public face of the administration's handling of Ukraine.' It is unclear whether Hunter Biden received government-sponsored travel or a protective detail for these endeavors."

WHOOPS: BIDEN CAMPAIGN TOUTS UKRAINIAN ANTI-CORRUPTION OFFICIAL WHO CALLED HUNTER BIDEN'S ACTIONS 'VERY BAD'

The letter sought information concerning "the protective detail that Hunter Biden received while his father was Vice President," as well as a "list of all dates and locations of travel, international and domestic, for Hunter Biden."

"In your response, please note whether his travel was on Air Force One or Two, or other government aircraft, as applicable and whether additional family members were present for each trip," the letter continues.

Government officials have long raised concerns about Hunter Biden's overseas dealings.

CLICK HERE FOR THE FOX NEWS APP

During the House impeachment proceedings last year, a career State Department employee testified that he had flagged Hunter Biden's apparent conflict of interest, but was told essentially not to bother the vice president's office.

Democrats have said Republicans were expressing interest in Hunter Biden's role with Burisma only because it could benefit them politically, given that they were aware of it for several years. But, commentators on both sides of the aisle have said, finger-pointing wouldn't excuse the Bidens' conduct.

"Impossible to justify $50k/month for Hunter Biden serving on a Ukrainian energy board w zero expertise unless he promised to sell access," political scientist Ian Bremmer previously tweeted.