By Maegan Vazquez and Sara Ganim, CNN

(CNN) -- The top Democrat on the House Oversight Committee accused Environmental Protection Agency Administrator Scott Pruitt of directing the EPA to prevent or delay public records requests from being processed.

In a letter sent to Pruitt on Monday, Rep. Elijah Cummings, D-Maryland, alleges that the EPA used a "first in, first out" approach to Freedom of Information Act requests -- granting responses to complex, Obama-era FOIA requests first and delaying simpler queries aimed at the current administration. The letter cites newly publicized interview transcripts between his committee and EPA staff.

Cummings writes that Kevin Chmielewski, Pruitt's former chief of staff, "informed staff from my office and several other congressional offices that you appear to be intentionally delaying the release of documents under FOIA relating to your tenure at EPA."

Another aide, Millan Hupp, confirmed Chmielewski's account in a subsequent committee interview. Hupp, according to the transcript, suggested Pruitt was privy to the "first in, first out" policy.

"Did the Administrator ever announce at a staff meeting that the Administrator's office should treat FOIA requests as first in, first out?" someone from the committee asks.

"I have heard discussions about that, yes," Hupp replies.

"With the Administrator?" Hupp is asked.

"He has made mention of it, yes," she responds.

The report states that Pruitt received pushback from at least one senior adviser.

CNN has reached out to the EPA and House Oversight Republicans for comment.

The letter comes as part of the oversight committee's investigation into Pruitt's actions as administrator. It's one of at least 13 inquiries into Pruitt's actions at the EPA.

The probes include reviews of his travel expenses, personal security, and other allegations of ethical concerns, such as Pruitt's below-market-rate lease with a lobbyist couple, one of whom represented a client before the EPA.

Pruitt and the EPA have largely defended his actions, saying decisions were made by his subordinates and that, in some cases, "processes will be changed going forward."

Cummings, in his new letter, writes that the orders from Pruitt "appear to directly contradict EPA's own FOIA regulations, as well as guidance issued by the Department of Justice."

"EPA regulations require the agency to use 'multitrack processing' in which simple requests are processed more quickly than complex requests. EPA regulations provide that if the agency determines that a request would be placed in the slower track, the agency would provide the requester with the opportunity to narrow the scope of the request," Cummings says.

Internal agency documents reviewed by the committee also show that the EPA established a process for political appointees to review responses to FOIA requests instead of leaving it to career employees.

Cummings writes that FOIA responses from the administrator's office have dramatically slowed since the start of Pruitt's tenure.

In the letter, Cummings tells Pruitt his "actions injecting politics into the FOIA process mark a stark departure from previous practice."

The ranking member then requested documents and communications related to the FOIA processes within the EPA, which are due in two weeks.