SHANGHAI (Reuters) - China will launch a campaign to track down the international origins of smuggled frozen meat as the country intensifies its campaign against the illegal trade after reports last month of smuggled "zombie meat" many years beyond its expiry date - some overdue for as much as 40 years.

Police and customs agents will work together to trace the smuggling routes from production to shop front in a bid to protect Chinese consumers and prevent the spread of disease, the country's food watchdog said in a statement on Sunday.

China is the world's top meat consumer, and industry insiders estimate that hundreds of thousands of tonnes of beef are smuggled into the country to fill a shortfall that is unmet by domestic production or approved imports.

"We will put all our strength into tracking the source and sale points of smuggled frozen meat, including those people orchestrating the process from behind the scene," the China Food and Drug Administration (CFDA) said.

The illegal trade caused a furore in June when the authorities said they had seized 100,000 tonnes of smuggled frozen meat worth around 3 billion yuan (S$653 million), some of which the official Xinhua news agency reported was as much as 40 years old.

Customs officials and the police denied there had been any recent busts involving meat that old, but said chicken claws dating back to 1967 had been seized in 2013.

The CFDA statement said meat around four to five years old had been seized this year.