China's imports of infant formula have continued to expand in recent years following increasing domestic demand with an increase of 24.8 percent year-on-year in the first half of this year, the General Administration of Customs said on Wednesday.

New Zealand, China's biggest import supplier of infant formula, provided 371,000 tons to China in the first half, up 34.3 percent year-on-year, Zheng Yuesheng, spokesman for the administration, told a news briefing.

Other import sources include France, Australia and the Netherlands, which accounted for about 8 percent of China's total imports in the first half.

Zheng said the import price of infant formula, mainly in bulk, remained stable in recent years and showed a declining trend in 2012 and the first half of this year.

On July 1, the National Development and Reform Commission, China's top economic planner, started an anti-trust investigation for alleged price fixing by transnational and local companies, including Switzerland-based Nestle SA's Wyeth, Mead Johnson Nutrition Co, Abbott Laboratories and Royal FrieslandCampina NV.