HONG KONG — One man made fake Honeywell N95 respirators at a makeshift factory on a farm. Pharmacies sold ineffective knockoffs of a Chinese version of Clorox. In one Chinese province, authorities seized more than seven million masks that were substandard, mislabeled or counterfeited.

China’s vast manufacturing machine has moved into overdrive to supply the country and the world with masks, testing kits, respirators and other gear to fight the global coronavirus pandemic. Companies big and small that once manufactured other items are now in the business of making anti-coronavirus gear — and regulators in China are struggling to enforce standards while encouraging the flow.

Those tensions blew into the open internationally this week. Officials in Spain said testing kits it bought from a Chinese company had only a 30 percent accuracy rate, rather than the 80 percent rate they had expected.

The Chinese embassy in Spain said in a series of tweets that the company that made the test kits, Shenzhen Bioeasy Biotechnology, had not been on Beijing’s list of certified providers nor a supplier to aid packages organized by Chinese companies like Alibaba, the e-commerce giant. Market regulators in Shenzhen, the southern Chinese city where the company is based, said they were investigating the matter.