Chinese consumers already wary of domestic milk powder brands fretted Monday whether they could find safe formula anywhere, after New Zealand dairy giant Fonterra issued a botulism alert.

Parents doing their shopping and users of China's popular Twitter-like service Sina Weibo cast around for who to trust and who to blame, although there were no reports of panic buying.

Three companies in China which were supplied by Fonterra, one of them a formula manufacturer, have been ordered to recall potentially tainted products.

"Babies who do not have breastmilk are so vulnerable," wrote a Weibo user using the handle L-Gao.

She added that she had given her newborn milk for a month from Dumex, a subsidiary of French foods giant Danone and one of the affected firms.

The other companies named were Hangzhou Wahaha and Coca-Cola's Chinese subsidiary.

Another user worried whether other brands were also at risk but had not yet been revealed.

The safety of baby formula became a sensitive issue in China after milk tainted with the chemical melamine left six children dead and sickened more than 300,000 in 2008.

Premier Li Keqiang pledged in March to punish safety violators and better oversee domestic milk powder production, in an effort to rebuild trust in Chinese companies.

Fonterra said there had been no reports of illness linked to consumption of the product, tainted with the bacteria Clostridium botulinum, which can cause botulism, an infection that can lead to paralysis and death.

Even after the Fonterra warning, some Chinese still placed their bets on foreign brands.

"No matter how bad imported milk is, I will never buy domestically made baby formula," said one Weibo user.

Others blamed the government, with another poster pointing out that "no department detected the problem or publicised it".

At a supermarket in Beijing, Shen Tingting, a businesswoman buying groceries, said she fed her 21-month-old daughter a local brand because her nephew had drunk it without any problems.

"I would consult my relatives before I buy baby formula -- I'd be more assured of its safety," she told AFP.