The World Health Organization rebuked Chinese officials Friday for withholding research that may link COVID-19’s origin to wild animals, asking why the data had not been made available three years ago and why it is now missing.

Before the Chinese data disappeared, an international team of virus experts downloaded and began analyzing the research, which appeared online in January. They say it supports the idea that the pandemic could have begun when illegally traded raccoon dogs infected humans at a Wuhan seafood market.

But the gene sequences were removed from a scientific database once the experts offered to collaborate on the analysis with their Chinese counterparts.