The Chinese city of Shenzhen told 100 major companies including iPhone maker Foxconn to set up "closed-loop" systems as it battles COVID-19, according to a document attributed to the local government circulating online on Monday. While Reuters could not independently verify the document, a notice at a Shenzhen office of oil giant CNOOC Ltd seen by Reuters said that the building would be closed for seven days until July 31, with staff to work from home and continue with daily COVID testing. A CNOOC spokesperson did not have an immediate comment. The Shenzhen government did not respond to a request…