An agency in Hunan province said that their previous tests showing that some imported baby formulas contain the banned additive are invalid, Xiaoxiang Morning Post reported Wednesday.

Xu, Party secretary of the School of Food Science and Technology at Hunan Agricultural University, admitted their errors in the testing and apologized to involved companies.

Test results from the Nutrition and Food Safety Testing Center of Hunan Agricultural University showed that vanillin, which can be harmful to baby's liver and kidney health, was found in Mead Johnson's 0-12months baby formula .The two tested batches of Mead Johnson's baby formulas were made on Oct 22, 2011 and April 18, 2012, respectively.

The additive was also found in products from baby formula makers including Abbott Laboratories and Wyeth, according to previous media reports.

Wyeth said there was no vanillin added in its formula for 0-12 month babies and it was willing to cooperate with official investigations.

The Administration for Industry and Commerce of Changsha, capital of Hunan, said it will conduct further investigations into the case.