A committee is already investigating if some White House staffers received high-level security.

A U.S. congressional committee on Monday demanded documents from the Trump administration relating to its overhaul of the background check process that determines who can handle America's secret information.

The House of Representatives Oversight Committee sent a letter to Mark Esper, the acting defence secretary, requesting documents and communications by July 8 relating to the ongoing overhaul, which some U.S. officials have said is disorganized and behind schedule.

The committee sent a separate letter demanding similar documents from the head of the U.S. Office of Personnel Management (OPM), which is transferring its background check responsibilities to the Pentagon under the Trump administration's plan. The committee also requested a briefing on the status of the project, which President Donald Trump outlined in an April 24 executive order.

"Troubling reports have emerged that the transfer may not be on track," the committee's letter said, saying there is "concern" that it may not occur by the Sept. 30 deadline given in Trump's order.

The letter was signed by the committee's chairman, Elijah Cummings, as well as two other Democrats, Representatives Stephen Lynch and Gerald Connolly.

Representatives of the OPM and the Defense Department did not immediately respond to requests for comment.

Security clearance background checks are a routine requirement for people hoping to be hired by the federal government and for contractors, as well as current employees.

Over the years, OPM has accumulated a backlog of more than 400,000 uncompleted clearance investigations, with some taking more than a year to finish, congressional experts said.

OPM, under Trump's order, is supposed to begin the transfer of 3,300 agency employees and 6,000 OPM contractors to the Defense Department by June 24.

Reuters reported on June 19 that the transfer of contractors to the Pentagon faced steep challenges.

"It's chaotic," one of the sources involved said. "People are trying to make it happen. But it's change on change on change, and this is the kind of thing that people run away from."

A senior Defense Department official told reporters on Monday that the agency was confident it would complete the transfer before October.

Another Defense Department official said that in the last year the government has reduced the backlog of clearance investigations and made "significant improvements" in the time it takes to get security clearances.

The House Oversight Committee is already investigating whether some staffers in Trump's White House received high-level security clearances over the objections of career officials, including Trump's daughter Ivanka Trump and his son-in-law, Jared Kushner.