Image copyright EPA Image caption Chinese authorities said unsafe meat was being smuggled from abroad and ending up in markets across the country

Chinese authorities have seized more than 100,000 tonnes of smuggled meat - some of it more than 40 years old, according to state media.

The frozen meat, estimated to be worth about £300 million (3bn yuan; $483m), was seized in a nationwide crackdown.

"It was smelly and I nearly threw up when I opened the door," an official from Hunan province, where 800 tonnes were seized, told the AFP news agency.

Poor standards have made food safety a major concern in China.

According to state newspaper the China Daily, officials from Guangxi, a southern region bordering Vietnam, found meat dating back to the 1970s.

Thawed several times

Some of the meat seized in Hunan province was found to have been refrozen after thawing out while in transit, according to the reports.

Yang Bo, an anti-smuggling official in Hunan province, was quoted as saying food was often transported in ordinary rather than refrigerated vehicles to save money. "So the meat has often thawed out several times before reaching customers," he said.

The Hunan province haul reportedly included beef, chicken feet and duck necks.

Authorities believe meat is smuggled into China via neighbouring Hong Kong and Vietnam, from countries such as Brazil and India, to sidestep import restrictions.

State media said 21 criminal gangs had been targeted by the police operation, with 20 people arrested in Hunan province alone.

News of the meat seizure came on the same day China's food safety watchdog asked three milk producers in Shaanxi province to recall infant formula powder.

Excessive nitrate levels were detected in some powdered milk samples and the products were branded as sub-standard, state media said.

The quality of milk products remains a sensitive topic in China after a deadly tainted milk scandal in 2008, when at least six children died and some 300,000 fell ill after consuming milk products contaminated by melamine.

The country has also faced criticism recently over a dog meat festival taking place this month, where about 10,000 dogs were expected to be slaughtered.