A pair of Republican senators announced a new stage in their investigation into possible corruption by the Biden family an hour after President Trump was acquitted of two articles of impeachment.

In a statement on Wednesday afternoon, Iowa Sen. Chuck Grassley and Wisconsin Sen. Ron Johnson said they "requested Hunter Biden’s official travel records from the U.S. Secret Service as a part of their ongoing probe into potential conflicts of interest."

The letter by Grassley, who is the chairman of the Finance Committee, and Johnson, the head of the Homeland Security and Governmental Affairs Committee, is the latest in a series of records requests by the pair scrutinizing Hunter Biden's lucrative business ventures abroad.

Hunter Biden is the 50-year-old son of former Vice President Joe Biden, who is now running for the Democratic presidential nomination, and a constant target of Republicans.

Impeachment proceedings began last year with the emergence of a whistleblower complaint about a July 25 phone call in which Trump urged Ukrainian President Volodymyr Zelensky to investigate his political rivals, including possible corruption involving the Bidens. Joe Biden has dubbed the allegations as “false, debunked conspiracy theories."

Trump and his allies have alleged the elder Biden inappropriately used the White House to convince Ukraine to lay off investigating Burisma, a Ukrainian natural gas firm that employed Hunter Biden. Republicans have also raised concerns about potential conflicts of interest to boost Hunter Biden's business ventures in China.

In their letter addressed to Secret Service Director James Murray, Grassley and Johnson requested information about whether Hunter Biden used government-sponsored travel to help conduct private business.

They asked for a description of the protective detail that Hunter Biden received while his father was vice president and "a list of all dates and locations of travel, international and domestic, for Hunter Biden while he received a protective detail. 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."

Grassley and Johnson asked that the Secret Service provide the requested information by Feb. 19.

A representative for the Secret Service did not immediately return a request for comment for this report.

Democrats accused Trump of improperly pressing Kyiv to announce investigations into the Bidens and others while leveraging nearly $400 million in military aid and a White House meeting. The House impeached Trump in December, but on Wednesday, the Senate voted 52-48 to acquit the president of the abuse of power charge and 53-47 to acquit the president of the obstruction of Congress charge.