US President Donald Trump said on Wednesday his government is trying to determine whether the coronavirus emanated from a lab in Wuhan, China, and Secretary of State Mike Pompeo said Beijing "needs to come clean" on what they know.

The source of the virus remains a mystery. General Mark Milley, chairman of the Joint Chiefs of Staff, said on Tuesday that US intelligence indicates that the coronavirus likely occurred naturally, as opposed to being created in a laboratory in China, but there is no certainty either way.

Fox News reported on Wednesday that the virus originated in a Wuhan laboratory not as a bioweapon, but 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 United States.

This report and others have suggested the Wuhan lab where virology experiments take place and lax safety standards there led to someone getting infected and appearing at a nearby "wet" market, where the virus began to spread.

At a White House news conference Trump was asked about the reports of the virus escaping from the Wuhan lab, and he said he was aware of them. "We are doing a very thorough examination of this horrible situation that happened," he said.