U.S. officials said early Tuesday they had been told AstraZeneca PLC may have released outdated information in its disclosure of trial results for its Covid-19 vaccine, which could have “provided an incomplete view of the efficacy data.”

The short statement came just hours after AstraZeneca released interim data from large-scale U.S. trials that it said found its Covid-19 vaccine to be 79% effective in preventing symptomatic disease. The release was seen as a vote of confidence in the shot, which has been clouded by uncertainty over its efficacy in earlier trials conducted in the U.K. last year and large-scale production problems. More recently, reported cases of unusual blood clotting in Europe raised concerns about the vaccine’s safety, though European regulators say it is safe.

In an unusual statement early Tuesday morning, the National Institute of Allergy and Infectious Diseases said an independent data monitoring board working with AstraZeneca in conducting its trials had raised concerns with the company’s data disclosure and urged it to work with it to ensure that the most accurate, up-to-date efficacy data would be made public.

The NIAID said the monitoring board, an independent body that works alongside a drug company to conduct trials, “expressed concern that AstraZeneca may have included outdated information from that trial.” The agency said it was urging AstraZeneca “to review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible.”

AstraZeneca wasn’t immediately available to comment early Tuesday.