The food safety regulator in the booming southern province of Guangdong on Wednesday said it had uncovered carcinogenic mildew-tainted cooking oil in the latest overhaul on food safety.

The carcinogenic mildew, called aflatoxin in scientific terminology, has triggered wide public concern over the safety of dairy products after being found in milk products from dairy giant Mengniu Dairy Group late last year.

The Guangdong Provincial Administration of Quality and Technology Supervision said in a statement that it found excessive amounts of aflatoxin in cooking oil products, mostly peanut cooking oil, made by 20 small companies.

Most of the cooking oil products were sold in bulk to nearby residents, it said, blaming lax screening over production materials for the food safety scare.

The agency also said it has revoked the production licenses of the 20 cooking oil makers and ordered them to recall the cancer-causing, mildew-tainted products.

Aflatoxin is produced by a fungus that commonly grows on crops such as grains and peanuts. High levels of the toxin have been shown to lead to cancer in animal tests.

Late last year, the mildew caught the nation's attention after it was found in high doses in dairy products from Mengniu. An initial investigation showed that the contamination was caused by mildewed feed given to cows in the dairy's plant in Sichuan Province.

Mengniu has issued a public apology in an online statement, but insisted that the problem was discovered before the tainted milk entered the market.