Internal U.S. Census Bureau documents indicate that it will be unable to meet a year-end deadline for handing in data used for allocating congressional seats as it deals with irregularities found in the numbers-crunching phase of the count, according to a Wednesday letter from the chair of the U.S. House committee that oversees the bureau.

The letter from Democratic U.S. Rep. Carolyn Maloney of New York, chair of the House Committee on Oversight and Reform, to U.S. Commerce Secretary Wilbur Ross accuses Republican President Donald Trump's administration of “a dangerous pattern of obstruction" in withholding documents about state population totals required to reallocate seats in the House.

Maloney wrote that the Commerce Department — which oversees the Census Bureau — missed a Nov. 24 deadline to give the documents to the committee. However, the committee has received internal bureau documents from an unnamed source that indicate that addressing the data anomalies “impacts overall end date by 20 days” and anticipates that the population count will not be complete until between Jan. 26 and Feb. 6, the letter said.

Those dates are significant because they would come after the inauguration of President-Elect Joe Biden on Jan. 20, likely leaving crucial decisions about the apportionment of congressional districts in the hands of a Democratic administration.

Maloney threatened a subpoena if “a full and unredacted set” of the requested documents are not given to the committee by Dec. 9. The Commerce Department did not immediately respond to requests for comment.

“By blocking the production of the full set of documents requested by the Committee last month, the Trump Administration is preventing Congress from verifying the scope of these anomalies, their impact on the accuracy of the Census, and the time professionals at the Census Bureau need to fix them,” the letter said. “Your failure to cooperate with the Committee’s investigation appears to be part of a dangerous pattern of obstruction with the Census.”

Missing the Dec. 31 deadline for turning in the apportionment numbers would be a blow to Trump’s unprecedented efforts to exclude people in the country illegally from being counted in the numbers used to determine how many congressional seats each state gets and how $1.5 trillion in federal spending is distributed.

Because of the coronavirus pandemic, the Census Bureau switched its deadline for wrapping up the once-a-decade head count of every U.S. resident from the end of July to the end of October. It also extended the deadline for turning in apportionment numbers from the end of December to the end of next April, giving bureau statisticians five months to crunch the numbers.

However, in late July and early August, officials at the Commerce Department announced field operations would finish at the end of September and the apportionment numbers would stick to a congressionally-mandated deadline of Dec. 31.

The Census Bureau already was facing a shortened schedule of two and a half months for processing the data collected during the 2020 census — about half the time originally planned. The bureau has not officially said what the anomalies were or publicly stated if there would be a new deadline for the apportionment numbers.

In a Nov. 19 statement, Census Bureau Director Steve Dillingham said processing anomalies have occurred in past censuses and he was directing the bureau to use all resources available to resolve the issues as quickly as possible.

One of the internal documents cited by Maloney is a Nov. 19 presentation for senior bureau officials that describes 13 anomalies that affect more than 900,000 census records. They include a problem related to duplicate non-response follow-up records in every state, a data error from the count of group quarters that affects more than 16,000 records, and a coding error affecting about 46,000 records in nine states.

The U.S. Supreme Court heard arguments this week in a case about Trump’s move to exclude people living in the country illegally from the population count.

Federal courts in California, Maryland and New York have ruled that Trump’s plan violates the Constitution, which provides that “representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State.” A fourth court, in Washington, D.C., held this past week that a similar challenge to the administration plan was premature, an argument that also has been made to the high court