The investigation focuses on Mary Kendall, acting inspector general at the Department of Interior, whom Vitter, Sessions and Cornyn said blocked a full investigation into manipulation of a National Academy of Engineers report by the White House and senior Interior officials.

After the oil spill, lawmakers asked the Department of Interior’s Office of the Inspector General to investigate the oil spill report that led to the moratorium.

On Thursday, Sessions, Vitter and Cornyn sent a letter to Inspectors General Integrity Committee Chairman Kevin Perkins with a survey of employees from the Interior Office to aid his investigation.

“The survey contains several concerning comments including one employee who stated: ‘I think there is widespread distrust and low morale in the organization right now. There are at least perceptions the acting IG and COS [chief of staff] did not do the right thing, ie [sic], improperly quashed investigations, and have not been forthright with Congress,’” the letter stated.

In the letter, the lawmakers expressed concern that the agency is being influenced politically.

“If the OIG at any federal agency fails to act as required, the public’s confidence in the proper governance of these agencies cannot be met,” Cornyn, Vitter and Sessions wrote. “These survey results seem to support the view that, at least within the OIG itself, there is a lack of full confidence in the integrity of their work under the current leadership. We believe this is important context for your ongoing investigation and reinforces why we believe it is important for your investigation to be thorough and concluded in a timely manner, as these matters need to be addressed and resolved without undue delay.”

The senators added that they hoped their survey results aid the investigation.