One video posted on a TikTok account belonging to a state-owned news outlet showed what it claimed was a street littered with antigen tests in a Chongqing industrial park.
"Sources say a labour dispute triggered conflict," the caption read. The video was taken down within hours.
Covid-19 infections have soared across China as the government moves away from its zero-tolerance approach to the virus, prompting a spike in demand for testing kits and drugs.
Authorities last month took over production lines at more than a dozen pharmaceutical firms, while some companies brought on new hires to meet surging demand.
Protests centred on labour issues and targeting individual companies occur frequently in China despite official efforts to clamp down on unrest.
Similar scenes unfolded at iPhone maker Foxconn's factory in central China last year, as furious workers unhappy with a Covid lockdown and pay dispute clashed with police.