China has refused to give the World Health Organization (WHO) raw data on its early COVID-19 cases, the Wall Street Journal reported on Friday, citing WHO investigators, who it said described heated exchanges over lack of detail.

The world health agency officials said raw, personalised data could help them determine how and when the coronavirus first spread in China, the newspaper said. 

"They showed us a couple of examples, but that's not the same as doing all of them, which is standard epidemiological investigation," Australian microbiologist Dominic Dwyer of the WHO's team told the paper.

"The interpretation of that data becomes more limited from our point of view."

The WHO is after details on 174 cases in particular from the early phase of the outbreak in Wuhan. 

All hypotheses are still open in the WHO's search for the origins of COVID-19, WHO Director-General Tedros Adhanom Ghebreyesus told a briefing on Friday, after Washington said it wants to review data from a WHO-led mission to China.

The mission, which spent four weeks in China looking into the origins of the COVID-19 outbreak, said this week that it was not looking further into the question of whether the virus escaped from a lab, which it considered highly unlikely.

The previous US administration of President Donald Trump, which left office last month, had said it suspected the virus may have escaped from a Chinese lab, which Beijing strongly denies.

"Some questions have been raised as to whether some hypotheses have been discarded. Having spoken with some members of the team, I wish to confirm that all hypotheses remain open and require further analysis and study," Tedros said.

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"Some of that work may lie outside the remit and scope of this mission. We have always said that this mission would not find all the answers, but it has added important information that takes us closer to understanding the origins of the COVID-19 virus," he said.

Tedros said a summary report of the mission's findings could emerge as early as next week, followed by a final report "in the coming weeks". Both would be made public.

The mission has said its main hypotheses are that the virus originated in a bat, although there are several possible scenarios for how it passed to humans, possibly first by infecting another species of animal.

The Trump administration has pointed fingers at a lab in the Chinese city of Wuhan, suggesting a virus being studied there may have escaped. China has long said the lab, the Wuhan Institute of Virology, never possessed the COVID-19 virus.

When pressed on why the mission did not believe a lab could have been the source, Peter Ben Embarek, the mission's head, told Friday's briefing that scientists from labs in Wuhan had told his team they didn't have it. If they had been studying it before the outbreak, he said, it would not have been a secret.

"Usually laboratory researchers who work and discover new viruses would immediately publish their findings. That's a common practice around the world, particularly with new, interesting viruses," he said. 

Reuters / Newshub.