The international expert mission to China all but ruled out a laboratory leak in a report, saying that COVID-19 probably passed to humans from a bat via an intermediary animal, media reports said on Monday.

But the report, drafted by World Health Organization-appointed international experts and their Chinese counterparts, offers no definitive answers on how the new coronavirus jumped to humans, AFP reported.

The expert report on the origins of COVID has had a troubled birth, with publication delays adding to the hold-ups and diplomatic wrangling that plagued the WHO’s attempts to get experts into Wuhan — the city at the centre of the initial outbreak.

They finally arrived on January 14, more than a year after the first cases surfaced.

Experts believe the SARS-CoV-2 virus that causes the COVID-19 disease originally came from bats.

The report authors judged that the most likely scenario was that it had made a direct leap to humans, while not ruling out other theories.

Beijing’s theory that the virus did not originate in China at all but was imported in frozen food was judged “possible” but very unlikely.

Claims promoted by former US president Donald Trump’s administration that the virus escaped from a research lab were judged “extremely unlikely”.

Meanwhile, UN Secretary-General Antonio Guterres called for a “new debt mechanism” allowing such options as debt swaps, buy-backs and cancellations to help worse-off countries.

Addressing an online forum that included dozens of world leaders, he said the pandemic has pushed the world to “the verge of a debt crisis” and required “urgent action”.

“We need to change the rules,” he argued.

The pandemic had also “shattered the lives” of millions of women and girls and reversed progress towards gender equality, he said.

COVID-19 has killed more than 2.7 million people worldwide in the 15 months since it emerged, forcing governments around the world to introduce restrictions that have battered the global economy.