Ten people, including eight Hong Kong locals and two Chinese mainlanders who illegally took 53 cans of milk powder out of the city, had been detained at entry ports by 2 pm, Friday, the first day a new regulation restricting milk powder purchases went into effect in Hong Kong, People's Daily reported.

The Import and Export Regulation 2013 stipulates that each person aged 16 or above can bring out of the region no more than 1.8 kilograms of powdered formula for children under 36 months, according to the Hong Kong Food and Health Bureau.

Anyone who flouts the rule faces a fine of HK$500,000 ($64,450) and two years in prison, it said on its website.

The regulation aims to ensure milk supply in Hong Kong following a surge in the number of Chinese mainlanders buying the formula due to the cheaper price and their trust in foreign brands, Wang Dingmian, former executive director of the Dairy Association of China, told the Global Times. The move will lead to rising prices in many stores, Wang said.

"It will make business tougher and I will have to improve the product price," Jiang Gefei, a man in Beijing who sells foreign formula milk on taobao.com, an online shopping website, told the Global Times.

Meanwhile, some residents in Shenzhen, Guangdong, a city neighboring Hong Kong, welcomed the new rule.

"I won't have to worry about too many Chinese mainland competitors buying the product in Hong Kong," one resident told the Global Times.

The regulation will not have a major impact on the mainland milk powder market, according to Wang.

Each year, milk formula brought from Hong Kong to the mainland is worth 800 million yuan, while the entire baby formula market in the mainland is worth about 40 billion yuan, said Wang.