US intelligence agencies are investigating mobile phone data which suggests the Wuhan Institute of Virology had an emergency shutdown back in October last year.
NBC News has reportedly obtained records which show that a "hazardous event" at the institute's high security National Biosafety Laboratory may have occurred between October 6 and 11.
This allegedly led to a shutdown of the P4 laboratory from October 7 to 24, during which there was no mobile activity, news.com.au reports.
The laboratory, located a short distance from the Wuhan wet market at the centre of the coronavirus outbreak, is the facility the Trump administration is blaming for starting the pandemic.