Chinese authorities say they have detained 19 people after at least 432 babies developed kidney stones blamed on contaminated milk powder.

A senior Health Ministry official told reporters Saturday that authorities ordered the Sanlu Group, which produced the contaminated milk powder, to stop production.

China's official Xinhua news agency said police are questioning 78 suspects in the city of Shijiazhuang, where Sanlu is based.

Investigators say dairy farmers may have added a dangerous chemical to milk linked to one infant death and the other illnesses.

Xinhua said Friday that investigators suspect farmers added the chemical to conceal that water added to the milk.  The chemical melamine would make the milk appear to have a higher protein content.

An official who is part of the nationwide probe said Friday that those responsible for the contamination will face severe punishment. 

The company blamed its suppliers for the contamination.  But a Chinese media report on Friday said Sanlu knew about the problem in August and decided not to inform the public. 

Sanlu waited until it became the target of a government investigation to announce that it found melamine in its products.  The company issued a recall on Thursday for about 700 tons of baby formula produced before August 6th.

Sanlu is a leading maker of dairy products and is partly owned by New Zealand company Fonterra.  Reports say some of the products could have made their way into overseas markets. 

Melamine is used in plastics, fertilizers and flame retardants.

Some information for this report provided by AP.