The Census Bureau acknowledged Thursday it ran into “anomalies” while processing data from this year’s decennial count, potentially jeopardizing President Donald Trump’s effort to exclude undocumented immigrants from census figures used to divvy up congressional seats.

Census Bureau Director Steven Dillingham said the agency ran into problems trying to finish tabulating census figures in time to be sent to the White House by a Dec. 31 deadline. Democrats in Congress and outside experts warned that finishing an accurate count may not be possible this year — or before Trump leaves office.

“During post-collection processing, certain processing anomalies have been discovered,” Dillingham said in a statement. “These types of processing anomalies have occurred in past censuses. I am directing the Census Bureau to utilize all resources available to resolve this as expeditiously as possible. As it has been all along, our goal remains an accurate and statistically sound Census.”

The agency originally planned on having five months to tabulate and check the data, but after the administration cut short the count, only two and a half months remained. The Census Bureau did not respond to questions Thursday about the nature of any delays or whether it would still deliver data by the end of the year.

House Oversight and Reform Chairwoman Carolyn B. Maloney accused the agency of keeping Democrats in the dark on census problems. In a letter sent to Dillingham on Thursday night, she cited documents leaked to the committee earlier this year that said the compressed schedule could undercut accuracy of the count.

“Today’s press reports indicate that the Census Bureau’s warnings in August were correct and that an accurate count — which the Constitution requires — cannot be produced for several more months,” Maloney said.

She asked Dillingham to provide the committee with any information produced for Commerce Secretary Wilbur Ross, who oversees the Census Bureau, about problems with the count and the agency’s handling of the reported “anomalies.”

After a Trump administration victory in court, Census Bureau officials ended data collection in October, leaving less than three months to finish tabulating and checking census results before the end-of-year deadline.

The flip-flopping on the census process came after the coronavirus pandemic forced the agency to delay in-person counting for several months. The agency then requested a 120-day deadline extension to allow counting through the end of October and deliver apportionment data in April.

The White House backtracked on that request after Trump launched an effort in July to exclude undocumented immigrants from apportionment. Advocates sued the administration to extend the count, and effectively won a two-week extension before a summary opinion from the Supreme Court let the administration wind down the count in October.

Last month, Census Bureau associate director Al Fontenot told reporters that the agency would deliver the apportionment data “as close as possible” to the end-of-year deadline. He said the census faced a “perfect storm” this year due to the coronavirus pandemic, wildfires and a record-breaking hurricane season that complicated the count.

“If we need more time to fix a problem that comes up that would impact the quality of the census, we’re taking it,” he said.

Terri Ann Lowenthal, a former House census committee staffer who now consults on census issues, said the apportionment issues should raise red flags for every member of Congress. Slim margins could determine the distribution of the last few congressional seats for states like Alabama, which is on the cusp of losing a seat.

“If the Census Bureau can’t take the time to make sure everyone is counted once and in the right place, the apportionment outcome could be skewed,” Lowenthal said.

The American Statistical Association and other outside groups have raised concerns that rushing the data processing could result in less accurate data. The association has called on the agency to release metrics for the accuracy of the census data.

Former Census Bureau Director John Thompson said that in 2000, the agency took from July to mid-December for data processing, a similar time frame to what the Census Bureau originally planned this year.

If the agency presses ahead to deliver the data by the end of the year, “I would be very concerned that the data would be substandard and contain inaccuracies,” Thompson said.

The effort to exclude undocumented immigrants from the apportionment process heads to the Supreme Court for oral arguments on Nov. 30. Three separate panels of federal judges rejected the administration’s attempt earlier this year, finding the effort violated the census statute, the Constitution or both.