BEIJING — Investigators believe dairy farmers added a dangerous chemical to milk that has been linked to kidney stones in dozens of babies and one death in China’s latest product safety scandal. The government vowed “serious punishment” on Friday after China’s biggest milk powder producer recalled 700 tons of baby formula. The official Xinhua News Agency said the powder was tainted with melamine, a toxic chemical used in plastics that contaminated pet food last year.

U.S. authorities warned American consumers to avoid all Chinese infant formula.

— From wire reports