The Justice Department on Thursday rejected document demands from the chairman of the House Oversight and Reform Committee related to the addition of a citizenship question to the 2020 census, which could lead to votes to hold Attorney General William Barr and Commerce Secretary Wilbur Ross in contempt of Congress.

In a letter from Assistant Attorney General Stephen E. Boyd, the department argued that some of the documents sought by the panel, such as letters between the DOJ and Census Bureau, are protected. The deadline to submit the documents, which are being sought under a subpoena, was Thursday.

“The committee’s insistence that the department immediately turn over these documents, in the face of a judicial order protecting them from disclosure, is improper,” the letter stated. The department said it has cooperated with the investigation into the addition of the citizenship question to the 2020 census.

Chairman Elijah E. Cummings of Maryland on Monday threatened Barr and Ross with contempt votes for not complying with subpoenas the committee issued in April. The panel could vote to hold them in contempt as early as next week as part of its push to obtain administration documents about the controversial addition of the question to the 2020 census.

The Commerce Department accused the committee of trying to influence Supreme Court litigation over the citizenship question, despite its cooperation with the panel investigation, according to a statement from a department spokesman.

“Holding the Secretary in contempt is an empty stunt, and it shows that the Committee is simply interested in playing politics,” the spokesman said.

A representative for the committee could not be immediately reached for comment Thursday.

The citizenship question has been challenged by a network of states and advocates who argue that the addition violated federal law. Three district judges agreed and the Trump administration appealed to the Supreme Court, saying that it needs the data from the question to enforce the Voting Rights Act and that federal law gives it the flexibility to add it.

Democrats have argued that the official reason for adding the question served as a smokescreen for its true purpose: suppressing noncitizen participation and gathering data to use in drawing Republican-leaning congressional maps.

They’ve leaned on revelations in citizenship question litigation being heard in New York that link deceased conservative redistricting strategist Thomas Hofeller to the origin of the question. In court papers, plaintiffs argued that Hofeller funneled the question to the Commerce Department, with the intent to gather enough information to draw congressional maps based on citizenship rather than population.

The Commerce Department and DOJ have rejected those allegations, arguing in court papers that the claims “border on frivolous,” and rely on speculation rather than hard evidence.

On Wednesday, the federal judge in the case set a briefing schedule for the new evidence related to Hofeller that would not put the allegations before the Supreme Court before it is expected to decide the case in the coming days.

The struggle between the committee and the administration has escalated over the past several months as Democrats have pushed to get more information about the origin of the question. On Wednesday, Democrats canceled planned subpoena votes for a trio of current and former Commerce Department officials after they agreed to closed-door interviews.

In April, Justice Department lawyer John Gore defied a committee subpoena to appear for testimony about the origin of the question.

Additionally, the full House is slated to vote on a measure next week to hold Barr in contempt over the full report from former special counsel Robert S. Mueller III. That resolution would allow Cummings to pursue a civil contempt lawsuit against Barr and Ross with the approval of a group of House leaders rather than a vote from the full chamber.