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(CNN) —  

The House Oversight Committee launched an ethics investigation Monday into Transportation Secretary Elaine Chao, who has recently faced scrutiny for her ties to an international shipping company run by members of her family.

Chairman Elijah Cummings, a Maryland Democrat, wrote in a letter to Chao, Cummings said he was investigating multiple allegations against the secretary, “including troubling questions about whether you are using your office to benefit you and your family.” The chairman also said he was probing Chao’s “failure to divest of stock” in a construction company whose board she used to sit on.

The investigation comes several months after Chao came under fire her connections to the shipping company, the Foremost Group, which is based in the US but has ties to China. The company was founded by Chao’s father and its current CEO is her sister. In June, CNN reported that Chao was receiving criticism from House Democrats and watchdogs who raised questions about whether Chao was using her position to benefit the company.

The investigation is the latest example of House Democrats using their oversight power to look into whether or not members of President Donald Trump’s Cabinet are acting unethically in their official roles. The probe could be met with resistance by the administration, as other congressional investigations have been in recent months.

In a statement to CNN on Tuesday, a DOT spokesperson acknowledged that the department received Cummings’ letter and that it was prepared to respond, adding, “Media attacks targeting the Secretary’s family are stale and only attempt to undermine her long career of public service.”

In the letter to Chao, Cummings notes that federal laws “prohibit federal employees from using their public offices for ‘the private gain of friends, relatives or persons with whom the employee is affiliated in a nongovernmental capacity.’”

The chairman cites a number of media reports that he says show how she has used her position to benefit the Foremost Group. In June, CNN reported that Chao has sat with her father for Chinese-language media interviews, appeared with him at an award ceremony and at a photoshoot listed on her schedule with him and other Foremost Group employees at the media center of the Department of Transportation, which oversees the US shipping industry.

CNN also found that Chao has accompanied her father or sister to more than a dozen events in China in roughly the last decade, which have included meetings with Chinese government officials. Chao’s financial disclosures show she holds no stake in the Foremost Group.

Rep. Raja Krishnamoorthi, an Illinois Democrat who sits on the committee, said Tuesday that Chao’s actions are part of a problematic pattern within the administration.

“Unfortunately, there’s a pattern in the Trump administration where Cabinet official after Cabinet official appears to be using their public office oftentimes for private gain. And that’s the concern here as well,” he told CNN’s Kate Bolduan on “At This Hour.”

The committee is asking Chao to turn over a slew of documents that span her time as secretary, including all communications between her and her father and sister, as well as all documents sent to or from department employees and Foremost Group employees.

The investigation is also looking into Chao’s “failure to divest of stock” from Vulcan Materials, a construction company whose board of directors she used to sit on, according to the letter. Though she pledged to sell her stock in the company, Chao maintained it until a Wall Street Journal report earlier this year revealed she hadn’t. In June, she divested from the company.

According to the letter, the committee will be probing Chao’s “actions that may have benefited the company in which (she) continued to hold shares, and (her) compliance with ethics and financial disclosure requirements.”

CNN’s Rene Marsh, Ellie Kaufman, Curt Devine, Drew Griffin, Yong Xiong and Lily Lee contributed to this report.