Health Minister Chen Zhu said Wednesday the third infant's death caused by the melamine-tainted formula occurred in southeastern Zhejiang province, but gave no details, Xinhua reported.
The other two babies -- one a 5-month-old body and other an 8-month-old girl -- died in northwest Gansu province of kidney failure after taking formula made by diary giant Sanlu Group.
More seriously, the contamination has been found in other brands besides those made by Sanlu.
The number of affected babies stood at 6,244 as of Wednesday. Of them, 158 had suffered acute kidney failure, the state-run news agency said.
Xinhua reported Chinese inspectors had found the chemical melamine in 69 batches of baby milk powder produced by 22 companies nationwide.
The Xinhua report said melamine is strictly forbidden in food processing, but quoted experts that it is added to raw milk to make its protein content appear higher.
The report said the Guangdong Yashili brand, the only one on the export list, was found to be melamine-free.
A BBC report said public outrage appearing on the Internet has now led to an official crackdown on media reporting of the problem.