HONG KONG — The Swiss food company Nestlé and its French rival, Danone, say they are cutting their prices of infant formula in China after Beijing began an investigation into possible price-fixing and anticompetitive behavior in the sale of milk powder.

Wyeth Nutrition, which Nestlé bought last year, said this week that it had been cooperating with the investigation by the National Development and Reform Commission of China and was responding by cutting prices and improving sales and marketing practices.

Danone, which has also acknowledged that its Dumex unit was cooperating with the Chinese commission, said in an e-mail statement that it was preparing a price cut proposal with details to be disclosed later.

Both companies, along with Mead Johnson Nutrition and Abbott Laboratories, said earlier this week that they were being investigated by the Chinese commission.