Federal authorities are examining whether Chinese companies deliberately restricted the world's production of storage containers for the shipping trade just before the COVID-19 pandemic began six years ago, sources with knowledge of the probe told CBS News.

Investigators have been looking at a handful of Chinese firms that together control the majority of unrefrigerated shipping container manufacturing around the globe, the sources said.

The companies in late 2019 slowed production by restricting the number of hours employees worked, which the investigators believed indicated a conspiracy to cut global supply and inflate prices, two of the sources said...

Several U.S. attorneys' offices, including the one in Maryland, have been conducting investigations related to the origins of the pandemic, according to a source with direct knowledge of the matter.

Last month, the first COVID-19 origins case emerged, after federal prosecutors in Maryland secured an indictment against David Morens, a former National Institute of Allergy and Infectious Diseases employee who is accused of trying to evade Freedom of Information Act requests in connection with COVID-19 research grants. He has pleaded not guilty...