China is preparing to test tens of thousands of blood samples collected from Wuhan residents as part of efforts to look into the origins of the pandemic-causing coronavirus, CNN reported Wednesday Beijing time, citing a Chinese official.

Photo shows a shopping street crowded with people in Wuhan, China, on April 4, 2021, about one year after the world's first coronavirus lockdown was lifted in the city around two and a half months after its imposition. (Kyodo) ==Kyodo

In a report, an international team of investigators from the World Health Organization who visited the central Chinese city in January and February has called for looking into whether blood bank samples collected during the initial period of the outbreak contain antibodies to the virus.

Chinese authorities first confirmed the virus in Wuhan in December 2019. It remains unknown how the virus started spreading. China has been criticized for not disclosing enough information or being sufficiently transparent as scientists have been working to understand the virus's origins.

The CNN report said up to 200,000 samples, including those from October and November 2019 when humans are likely to have first been infected with the virus, are kept at a blood center in Wuhan.

An official from the country's National Health Commission told CNN that testing would happen once a two-year storage limit expires for the relevant blood samples.