The Associated Press reports that four babies have died and almost 53,000 have been sickened from melamine in baby formula in China that now appears to date back to Dec. 2007.

An investigation by the State Council, China’s Cabinet, has found that for eight months, China’s biggest producer of powdered milk, Sanlu Group Co. “did not inform the government and did not take proper measures, therefore making the situation worse.”

Melamine, which can cause kidney stones and kidney failure in babies, has since been found in infant formula and other milk products from 22 of China’s dairy companies.

Also, Li Changjiang, who headed the General Administration of Quality Supervision, Inspection and Quarantine since 2001, has resigned, a year after he and the government promised to overhaul the system.