The U.S. Census Bureau says the data irregularities that are putting in jeopardy a year-end deadline for turning in numbers used for divvying up congressional seats affect only a tiny percentage of the records and are being resolved as quickly as possible.

The statistical agency’s statement was issued as the House Committee on Oversight and Reform held a hearing Thursday on the data abnormalities, which likely will force a delay in when the Census Bureau turns in the apportionment numbers, to several weeks past a Dec. 31 deadline.

The timeline remains in flux for turning in the apportionment numbers used for deciding how many congressional seats and Electoral College votes each state gets in future elections, the Census Bureau said in a statement late Wednesday.

“These kinds of anomalies and issues are expected and are similar to the Census Bureau’s experience in prior decennial censuses,” the bureau said. “What is certain is that the Census Bureau is working to thoroughly correct and address all issues and anomalies as a part of its mission to deliver accurate 2020 Census data products as close to the statutory deadline as possible.”