Leading Republican senators are asking the State Department to turn over all information relating to Hunter Biden and his business associates after newly released documents revealed that foreign companies attempted to leverage their ties to former vice president Joe Biden’s son.

Sens. Ron Johnson (R., Wis.) and Chuck Grassley (R., Iowa), chairmen of the Committee on Homeland Security and Governmental Affairs and the Committee on Finance, respectively, sent a letter to Secretary of State Mike Pompeo asking for all records related to Hunter Biden, his business partners, and their companies on Thursday. The letter also requests information about Biden’s Ukraine dealings after documents emerged showing that a lobbyist for Burisma, an energy firm that paid Hunter Biden to serve on its board, dropped Biden’s name in emails to government officials.

The senators said the reports raise concerns about potential conflicts of interest. The documents would help lawmakers “better understand what actions, if any, the Obama administration took to ensure that policy decisions relating to Ukraine and Burisma were not improperly influenced by the employment and financial interests of family members,” the letter said.

Hunter Biden’s lucrative dealings with foreign companies during the Obama administration have become a source of controversy for Democratic presidential frontrunner Joe Biden. In October, three different agencies briefed Grassley staffers about the Obama administration’s approval of a business deal involving Hunter Biden and a Chinese firm that previously stole U.S. military technology, the Free Beacon previously reported.

Investigative journalist John Solomon first obtained the internal documents through a Freedom of Information Act request. The documents revealed that Karen Tramontano, a top Burisma lobbyist from Blue Star Strategies, name-dropped the vice president’s son in an attempt to arrange a meeting between company officials and Undersecretary of State Catherine Novelli.

Tramontano “noted that two high profile U.S. citizens are affiliated with the company (including Hunter Biden as a board member),” a department official wrote in a February 2016 email. A meeting between Tramontano and Novelli was subsequently scheduled for March 1, 2016.

The email exchange took place as British and Ukrainian authorities investigated the owner of Burisma for criminal wrongdoing. Tramontano told the State Department official she believed Burisma was innocent and that the meeting would give the administration a “better understanding of how the U.S. came to the determination that the company is corrupt,” according to the newly released emails.

The documents also showed that Devon Archer, Hunter Biden’s business associate and fellow Burisma board member, was scheduled to meet then-secretary of state John Kerry one day after the Tramontano meeting. Archer was a former business partner of Kerry’s stepson, Chris Heinz.

A Heinz spokesman told the Washington Free Beacon that his client cut ties with Archer and Biden over concerns about their relationship with Burisma.

“Mr. Heinz strongly warned Mr. Archer that working with Burisma was unacceptable,” said Chris Bastardi, a vice president at Sunshine Sachs, in a statement to the Free Beacon. “Mr. Archer stated that he and Hunter Biden intended to pursue the opportunity as individuals, not as part of the firm. The lack of judgment in this matter was a major catalyst for Mr. Heinz ending his business relationships with Mr. Archer and Mr. Biden.”

Johnson and Grassley requested all information regarding both the Tramontano meeting and the Archer meeting, as well as a pair of 2015 meetings between Hunter Biden and then-deputy secretary of state Anthony Blinken. The details of those arrangements were discussed in the emails obtained by Solomon.

“In light of the information recently released via FOIA and referenced in the letter, the senators are seeking additional details on any further actions by the State Department,” finance committee spokesman Taylor Foy told the Washington Free Beacon.

The letter focuses on Hunter Biden’s Ukraine dealings, but could unearth details about his other foreign business relationships. The letter explicitly requests information about Rosemont Seneca Bohai, a company that partnered with Chinese financiers during the Obama administration. Bohai paid Hunter Biden $700,000 between 2014 and 2015, according to the Daily Caller.