Top Chinese beer maker Tsingtao Brewery, said on Monday it had alerted police and taken steps to prevent contamination after a video apparently showing a worker urinating into a container of beer ingredients went viral.

The video, which showed a warehouse worker in blue overalls and a yellow hat climbing into a container and urinating on the contents, has racked up tens of thousands of views on China's microblogging site Weibo since appearing last Thursday and triggered food safety concerns among netizens.

Reuters could not verify the authenticity of the video.

"Now that he is being filmed and posted online, has he ever had this behaviour of urinating into raw ingredients before?" one user commented.

"The problem is how to assure the public that the existing beer raw materials are not contaminated," wrote another.

Shanghai-listed Tsingtao's shares tumbled as much as 7.5% in early Monday trade, before recovering to close down 0.37%.

Tsingtao said in a filing to the Shanghai stock exchange that it "attaches great importance" to the incident and that the security authorities were currently investigating.

"The batch of malt in question is completely sealed," Tsingtao said, adding the company's production and operation continued as normal.

Also Read: China acknowledges Israel’s right to self-defence