One of China's biggest beermakers says it has opened an investigation after a video appearing to show a factory employee urinating on raw ingredients went viral this week.

The clip, published online on Thursday, purportedly shows a male worker at a Tsingtao Brewery Co. warehouse clambering into a high-walled container and relieving himself onto its contents.

The footage circulated widely on Chinese social media, racking up tens of millions of views on the popular platform Weibo.

Tsingtao said on Friday that it had contacted the police over the incident and an investigation was ongoing.

"Our company attaches high importance to the relevant video that emerged from Tsingtao Brewery No. 3 on 19 October" the beermaker said in a statement.

"We reported the incident to the police at the earliest opportunity, and public security organs are involved in the investigation," it added.

"At present, the batch of malt in question has been completely sealed. The company continues to strengthen its management procedures and ensure product quality."

Tsingtao, China's second-largest brewer, is one of the country's best-known beverage brands, and its tall bottles of crisp lager are a fixture of bars and restaurants across East Asia.

In recent years, the Hong Kong-listed company has sought to capitalize on the changing tastes of younger Chinese drinkers by diversifying into craft ales and other products.

WITH AFP