A paper posted recently suggests that genetic data from soil samples sent to a Chinese firm for sequencing could have been contaminated by an ancestor of the Covid-19 virus. The Wuhan Institute of Virology (WIV), where some scientists believe the pandemic likely began, has used the same firm.

If the samples were analyzed in early 2020, it’s possible they became contaminated when other scientists were studying Covid-19 as it began to spread. But it would be suspicious if the analysis was done before the end of December 2019, when China says it first identified the virus.

The Hungarian research article is a preprint, or early manuscript that hasn’t been peer reviewed, and some scientists are already contesting its importance. While a lab origin of Covid-19 has become more plausible over time, some developments proved underwhelming on closer examination.