"These documents indicate that you may have improperly omitted Darling from your financial disclosure, and they raise concerns that you may have failed to identify other clients who paid for your service as a lobbyist during the period covered by your disclosure report," House Oversight chairman Elijah Cummings wrote in a letter to Wheeler informing him of the investigation.

Darling supplies ingredients for fertilizers, fuel and pet and livestock food, among other products, according to The Hill.

Wheeler also met with Darling in June 2018, while he was serving as deputy administrator at the EPA, according to CNN, but an agency lawyer said this did not violate ethics laws. The EPA did not comment on the investigation to the media and instead said it would respond through the "proper channels," according to CNN.

The DOI Six

Six officials at the DOI are being investigated by the department's Office of Inspector General over meetings with former employers or clients on department-related business, The Washington Post reported Tuesday.

President Donald Trump signed an executive order early in his term saying all appointees must recuse themselves from matters involving former clients for two years. But the Campaign Legal Center sent a letter to the DOI watchdog in February detailing how six officials had violated that pledge. The Office of Inspector General wrote back to the center April 18 to say an investigation was in process.

"The department takes ethics issues seriously," Interior spokeswoman Faith Vander Voort told The Washington Post in an email.

The letter was sent three days after the Office of Inspector General announced it was opening an investigation into newly-confirmed Interior Secretary David Bernhardt after receiving various complaints about his potential conflicts of interest, The Washington Post reported April 15. Bernhardt replaced Ryan Zinke, who resigned as Interior Secretary after an ethics investigation into his conduct was passed on to the Justice Department.

Federal law requires officials to disclose any client over the past two years that paid them more than $5,000 ...Andrew Wheeler apparently failed to disclose a former lobbying client that paid him more than $5,000https://thehill.com/policy/energy-environment/440299-epa-administrator-failed-to-disclose-former-lobbying-client …

Here is a brief outline of officials implicated in the most recent investigation, as summarized in The Huffington Post.

1. White House liaison Lori Mashburn, who attended two private events hosted by her former employer and right-wing think tank the Heritage Foundation
2. Senior Deputy Director for Intergovernmental and External Affairs. Ben Cassidy, who participated in agency meetings on issues he had lobbied the department about on behalf of the National Rifle Association, including trophy hunting and the designation of national monuments
3. Assistant Secretary for Insular and International Affairs Doug Domenech, who met with his former employers, a Koch-link think tank called the Texas Public Policy Foundation, about issues over which the foundation was suing DOI
4. Former Energy Counselor to Zinke Vincent DeVito, who attended a meeting with a former energy client
5. Deputy Director of Interior's Office of Intergovernmental and External Affairs Timothy Williams, who participated in a video call with his former employer, who is vice president of the Koch-funded Americans for Prosperity
6. Director of Interior's External Affairs Office Todd Wynn, who had a phone call with a committee member of the oil-funded Council of State Governments, of which he had also been a committee member before taking the DOI job

"An agency's ethical culture depends on ethical leadership. Former Secretary Ryan Zinke and Secretary David Bernhardt, now under investigation himself for ethics violations, have failed to demonstrate adequate ethical behavior at the top of Interior," Matsco said in a statement reported by The Huffington Post. "We hope this investigation will answer whether these officials are working on behalf of the American people or on behalf of the interests that used to pay their salary."