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LONDON, March 12 (Xinhua) -- The novel coronavirus is "extremely unlikely" to have leaked from a Chinese laboratory, Dutch virologist Marion Koopmans has said after a tour to the central Chinese city of Wuhan to investigate the origin of COVID-19.

At the beginning of 2021, a team of experts appointed by the World Health Organization (WHO) completed a 28-day mission to Wuhan to investigate the origins of the virus that has caused the global COVID-19 pandemic.

After visiting three labs in Wuhan, including the one close to the Huanan seafood market and the Wuhan Institute of Virology and discussing their research programs, the way they work and health monitoring of their staff, they concluded that "it's extremely unlikely that there was a lab incidence," Koopmans said Wednesday in a video dialogue published on the website of Chatham House, a London-headquartered policy institute.

"We can not work on the basis of speculation; we work on the basis of the observations that we have," she said, shattering the lab-leak theory and calling for science-based approaches.

The scientist said the team does not completely rule out the possibility that the coronavirus could be spread by packaging on frozen food, mentioning a former experiment in which the virus could still be cultured back after being put on a fish and stored in a fridge for three weeks.