Immigration court data released by the Department of Justice has contained "gross irregularities" and the agency appears to have "silently but systematically" deleted nearly a million records, a nonprofit research organization said in a report accusing the agency of mishandling data it releases to the public.

Those issues could have grave implications because policymakers, judges and the public rely on the data to make decisions, the Transactional Records Access Clearinghouse, a nonpartisan research center housed at Syracuse University, said in the report released Thursday .

Through ongoing Freedom of Information Act requests, TRAC routinely receives from the Justice Department's Executive Office for Immigration Review, which oversees the U.S. immigration court system. The research group is well-respected among policymakers, reporters and researchers, and it frequently publishes data analysis and reports on several topics, including immigration.

TRAC said it noticed discrepancies in data it obtained from the office earlier this month and began to look into those issues. By analyzing the most recent batch of data on immigration court records and filings it received as well as previous batches, TRAC determined that it appeared the agency was both unintentionally and intentionally deleting records from the data releases. This led to concerns that the office was deleting records from its master database.

The issues are "substantive, ongoing and in need of prompt attention," TRAC said.

The Executive Office for Immigration Review disputed TRAC's findings.

"TRAC does not disclose their methodology and to the best of our knowledge, the EOIR data release is accurate and up-to-date. The EOIR database is updated in real time, and case identifiers may change according to developments in a particular case," a spokesperson for the office said. "Further, TRAC’s requests are handled by our FOIA office staffed by career officials. EOIR does not delete records. Records that TRAC claims are 'deleted' are simply withheld from release to TRAC under a FOIA exemption."

TRAC said it was particularly concerned with what it saw as the office's refusal to work with the group to ensure the accuracy of the data.

TRAC notified the office of the data issues when it first spotted them and officials promised to look into it, TRAC said. After some back and forth, however, the agency "dug in its heels," TRAC said.

Last week, the agency told TRAC that the FOIA process "does not require the Agency to create records in response to your specific questions, nor to certify the accuracy of data contained in responsive documents," TRAC said.

After that exchange, TRAC said it decided to publicize its observations.

Because the office's data is "relied upon as part of the official record of court filings and proceedings that have taken place, one should not expect official records to simply go missing without explanation," TRAC said. "It is deeply troubling that rather than working cooperatively with TRAC to clear up the reasons for these unexplained disappearances, the agency has decided to dig in its heels and insist the public is not entitled to have answers to why records are missing from the data EOIR releases to the public."

TRAC noted that the office's data has been inaccurate in the past. The Supreme Court relied on figures from the agency when issuing a ruling on a case affecting U.S. Immigration and Customs Enforcement detention practices.