US President Joe Biden ordered aides to find answers to the origin of the virus that causes Covid-19, saying on Wednesday that US intelligence agencies are pursuing rival theories potentially including the possibility of a laboratory accident in China.

Intelligence agencies are considering two likely scenarios but still lack strong confidence in their conclusions and are hotly debating which is more probable, Biden said.

The conclusions were detailed in a report to Biden, who asked his team in March to detail whether the novel coronavirus "emerged from human contact with an infected animal or from a laboratory accident," according to the president's written statement.