BEIJING -- Authorities have found the industrial chemical melamine in baby formula made by 22 producers, suggesting China's problems with tainted baby formula extend far beyond the single company implicated to date.

The Chinese government early Wednesday increased its estimate of the number of babies sickened by the tainted formula to 6,244, including 158 who have acute kidney failure. The Ministry of Health also reported a third infant death in the widening scandal, which has again highlighted China's weak control over food...