Did the coronavirus escape from a Chinese lab in Wuhan, or did it come from an animal source in a wet market?

US intelligence officials are determined to solve this riddle by any means possible, and the investigation may only be in its early stages.

National security officials confirmed the United States government is looking into the possibility that the novel coronavirus originated in a Chinese laboratory rather than a market, according to multiple sources familiar with the matter, CNN reported.

The theory is one of multiple being pursued by investigators as they attempt to determine the origin of the coronavirus that has resulted in a pandemic and killed hundreds of thousands, the report said.

The US does not believe the virus was associated with bioweapons research, and officials noted that the intelligence community is also exploring a range of other theories regarding the origination of the virus, according to an intelligence source.

The action comes after intelligence sources told Fox News that “patient zero” worked at the Wuhan lab, and spread the virus into the local population after leaving work.

The lab theory has been pushed by supporters of President Donald Trump, including some congressional Republicans, who are eager to deflect criticisms of Trump’s mishandling of the pandemic, the report said.

Secretary of State Mike Pompeo also called on Beijing “to come clean” on what it knows, ratcheting up the pressure on China.

“What we do know is we know that this virus originated in Wuhan, China,” Pompeo told Fox News.

“We know there is the Wuhan Institute of Virology just a handful of miles away from where the wet market was. There is still lots to learn. The United States government is working diligently to figure it out.”

Other sources told CNN that US intelligence hasn’t been able to corroborate the theory but is trying to discern whether someone was infected in the lab through an accident or poor handling of materials and may have then infected others, the report said.

Another theory floating around Langley is that a poorly paid lab worker, in a bid to make extra money, sold a dead test animal at the wet market, instead of incinerating it.

Joint Chief of Staff Chairman Mark Milley acknowledged this week that US intelligence is taking “a hard look” at the question of whether the coronavirus originated in a lab.

“I would just say, at this point, it’s inconclusive although the weight of evidence seems to indicate natural (origin). But we don’t know for certain,” Milley told reporters.

Asked about the intelligence, which was first reported by Fox News, President Trump said on Wednesday that the US is “doing a very thorough examination of this horrible situation that happened” but refused to discuss what he had been told.

The lab theory has been strongly denied by the Chinese government and many outside experts have also cast doubt on the idea, claiming that scientific evidence does not support a laboratory construct or a purposefully manipulated virus.

Scientists back two popular theories: (i) natural selection in an animal host before zoonotic transfer; and (ii) natural selection in humans following zoonotic transfer.

China’s foreign ministry noted on Thursday the World Health Organization has said there is no evidence coronavirus was made in a lab.

Fox News claimed on Wednesday that the virus originated in a Wuhan laboratory as part of China’s effort to demonstrate that its efforts to identify and combat viruses are equal to or greater than the capabilities of the US.

This may be the “costliest government cover-up of all time,” one of the Fox sources said.

The sources believe the initial transmission of the virus was bat-to-human – a naturally occurring strain that was being studied there – and that “patient zero” worked at the laboratory, then went into the population in Wuhan.

The “increasing confidence” comes from classified and open-source documents and evidence, the sources said. Fox News has requested to see the evidence directly.

The Wuhan lab is China’s only bio-safety level four (BSL-4) facility, and has long been eyed with suspicion as scientists try to determine how the deadly virus crossed over into humans, the UK’s Daily Mail reported.