One of China's biggest beermakers said it had 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 October 19," 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."

Many social media users reacted to the video with anger and voiced support for one of China's best-known beverage brands.

"I suggest the company takes this man to court and gets him to pay compensation for the damages," read one popular Weibo response to the company's statement.

"Investigate this thoroughly! Always stand up for our national champion brands!" wrote another user.

Hong Kong-listed Tsingtao is China's second-largest brewer, and its tall bottles of crisp lager are perennial fridge-fillers in bars across East Asia.

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

Some web users were not about to pass up the chance to make a wry quip about the country's famously light and fizzy mass-market brews.

"I've always said the beer here is like horse pee. Turns out I was wrong," one of them commented.

"Thanks, I think I'll have wine instead," quipped another.