The liberal watchdog group Citizens for Responsibility and Ethics in Washington (CREW) filed a lawsuit against the Department of the Treasury on Monday for failing to respond to a Freedom of Information Act (FOIA) request the group filed last month.

CREW filed a FOIA request with the Treasury Department on Aug. 23 requesting documents related to the Treasury Secretary Steven Mnuchin and his wife Louise Linton’s use of a government plane to travel to Lexington, Kentucky on Aug. 21.

The pair traveled to the state to visit Fort Knox with Senator Majority Leader Mitch McConnell (R-KY) and view the solar eclipse on-site. They also made an appearance at a luncheon with members of a local chamber of commerce, The Washington Post reported last month.

The trip gained national attention after Linton, a private citizen, posted a picture on Instagram of herself and Mnuchin exiting a government plane, where she tagged several high-end designers in various pieces of her clothing. Followers responded by criticizing Linton for being out of touch. Linton lashed out, mocking one of the commenters and bragging about her and her husband’s wealth.

While McConnell’s office originally said that Mnuchin, Linton and McConnell viewed the solar eclipse from the roof of Fort Knox just outside the path of totality, his team later changed the story, editing a caption on a photo of the trio on Facebook and issuing a statement saying they watched the eclipse from the lawn.

That, coupled with Linton’s social media post, was what prompted CREW to file a FOIA request for records related to Mnuchin’s use of a government plane for the Aug. 21 trip, as well as documents concerning authorization for and cost of using government planes for “any purpose since his appointment as Treasury Secretary,” according to the lawsuit.

The group made an “expedited request” for the documents because of the widespread media interest in the topic at the time, according to the suit. The Department of the Treasury not only failed to comply with the request, it didn’t even respond, according to CREW’s suit.

“If Linton, a private citizen, used government resources to view the eclipse or if Secretary Mnuchin used government resources for personal purposes, the American people deserve to know all they can about the decision to use taxpayer resources instead of a commercial flight,” CREW officials said in a statement released Monday.

Governmental agencies are required to respond to FOIA requests within 20 working days of their filing, and agencies must respond to expedited requests within 10 days, according to the lawsuit.

“We’re suing because the government has so far failed to even respond,” CREW Executive Director Noah Bookbinder said in a statement. “At a time of expected deep cuts to the federal budget, the taxpayers have a significant interest in learning the extent to which Secretary Mnuchin has used government planes for travel in lieu of commercial planes, and the justification for that use.”

A spokesperson for Department of the Treasury said the agency does not comment on litigation.

The lawsuit asks that the Treasury “immediately and fully process” CREW’s Aug. 23 expedited FOIA request and “disclose all non-exempt documents immediately.” It also asked the department to pay CREW’s attorney’s fees.

A Treasury source familiar with the lawsuit told TPM that the agency’s “FOIA office has received and is responding to the request.”

Read the full lawsuit below: