Tons of melamine-contaminated milk powder have been discovered at a Chinese ice cream factory three years after widespread use of the chemical in infant formula killed six babies.
The discovery underscores China's continuing problems with illegal food additives used to make a quick profit regardless of the health risks.
Caches of toxic milk powder have repeatedly been discovered since a crackdown in 2008 that saw dozens arrested and a dairy farmer and a milk salesman executed.
Police in the southern city of Chongqing said the Jixida Food Company bought 26 tons of the milk powder a year ago to make pastries and ice cream.
It was stored in a warehouse and had not yet been used. Five suspects were detained and three could face criminal charges.
Adding melamine and water to milk and milk products makes the tainted, weaker products appear to have the correct protein content. Health problems from the industrial chemical include kidney stones and kidney damage.
At least six children died and nearly 300,000 children fell ill after consuming contaminated infant formula in 2008.
The scandal prompted China to pass tougher food safety regulations and step up inspections.
A recent spate of new problems prompted the State Council, China's cabinet, to order a renewed crackdown on the illegal food additives last week.
So far this year, authorities have uncovered sales of drug-tainted pork, bean sprouts treated with a carcinogenic chemical compound, and old bread treated with sweeteners and dye to make it seem fresh.