The figure is five times higher than previously announced.
Mr Chen said a third baby had now died - with the latest fatality occurring in the Zhejiang province of eastern China.
Twenty-two brands of powder were found to contain the toxic industrial chemical melamine, apparently added to make it appear higher in protein.
Mr Chen said a total of 6,244 infants were now sick, and that the number of those diagnosed with "acute kidney failure" had risen to 158.
Anger on forums
The government has labelled the poisonings a "level one" food safety incident and formed an emergency team to grapple with the fallout.
It is keen to try to reassure parents that it is in control of what is happening, says the BBC's James Reynolds in Beijing.
This scandal has undermined confidence in food safety in China and many parents are worried about what they will feed their babies, he adds.
Rising public anger, expressed on China's active internet forums, is prompting reports of a crackdown by the government on reporting of the scandal.
Four people have so far been arrested, with more expected. Twenty-two others are being questioned.
