The website of dairy giant China Mengniu Dairy Co. was hacked late Wednesday night after the company revealed that the mildewed feed given to cows caused the high levels of a cancer-causing toxin found in its milk.

The hacker changed the name of Mengniu's website to "Hacked By: Drift" and left a message saying: "Mengniu once made the Chinese people strong and once made the Chinese proud, yet now this dairy company is doing harm to its own people. We are family, but you are hurting your own family members. Do you even have a conscience?"

On December 24, China's quality watchdog found excessive levels of flavacin M1 in a batch of Mengniu milk products during a random inspection.

Shares of Mengniu declined 23.95 percent and closed at HK$20 on Wednesday, the biggest decline since September 2008.

China's business press carried the story above on Thursday.