As the frozen meat thawed and began to rot, Agriculture, Fisheries and Conservation Department workers launched massive cleanup operations to save tourist destinations and prevent health hazards.

In the past month, officers in the eastern and northern divisions of the marine police have intercepted five vessels and seized more than 13,000 boxes of meat, some of it from Brazil and Canada. Some boats that were not detained turned back to Chai Wan carrying up to 125 tonnes of thawing meat.

These boats were not seized because a successful operation means difficulties for policemen: what do they do with large cargoes of swiftly thawing meat?

'It's a major problem,' said Superintendent Glyn Davies, officer in charge of the eastern division. Last Tuesday two cargo vessels, one laden with 1,000 boxes of frozen cow's stomachs, were stopped off the Sai Kung coast. On some recent nights police intercepted as many as 10 vessels.

Based at Tui Min Hoi, Sai Kung, The fleet led by Mr Davies patrols nightly.

'Meat smuggling is a highly organised operation,' he said. 'Every night, large converted trawlers up to 25 metres long put out of Chai Wan heavily laden with hundreds of tonnes of frozen meat.'

The trawlers rendezvous with fleets of sampans, mostly from the mainland, and transship cargoes at sea.

But these vessels are often so heavily laden with hundreds of boxes of frozen meat that they run into trouble in the swells and waves kicked up in Mirs Bay by strong northeasterly winds.

That's why so many have run into trouble recently.

'It's not simply a matter of shipping unmanifested cargo.

'There's also the element of danger to shipping, not to mention the risks marine police take trying to intercept vessels illegally in Hong Kong waters,' Mr Davies said.

Last week in Tai Long Wan a policeman narrowly escaped serious injury when he boarded one grounded vessel.

'It's a major industry. One night recently, there were alerts for 50 HST [high speed targets] as a flotilla of vessels with powerful outboard engines sped over Mirs Bay to join the meat-laden mother ships heading out of Chai Wan.'

In cases like this, police have adopted frustration tactics.

They turn on lights and follow the large and powerful, but slower, trawlers laden with meat.

Knowing they are under surveillance and cannot unload, the trawlers return to port and the speedboats head back to the mainland.

'It's a well-organised racket involving scores of people receiving the meat in Hong Kong, loading it onto mother ships in Chai Wan, then meeting fleets of illegal boats that come into Hong Kong from China,' said Mr Davies.

'It's obviously profitable, otherwise people would not be putting so much work and money in.'

What happens to the tonnes of frozen meat aboard the trawlers, which are not refrigerated?

'It doesn't bear thinking about.

'Obviously, after several hours on a trawler on the open sea, the meat is going to thaw.

'The potential health hazards for customers in China are frightening.'

The Hong Kong government has been in touch with the Guangdong authorities about the rackets.

On February 3 one vessel ran aground at Tai Long Tsui near the remote Tai Long Wan beach.

Environmental campaigner Charlie Frew said: 'It was a major ecological disaster.'

Mr Frew saw beaches covered with a thick layer of rotting chicken legs and other meat.

'The smell was revolting. Nobody could possibly swim there. People retreated from the beach in horror.'

A major cleanup was launched by Agriculture, Fisheries and Conservation Department.

A 19-metre-long Hong Kong- registered boat grounded and broke up in the same area on February 12, leaving the waves to scatter chicken wings, chicken thighs and ox tripe, together with the wreckage of the vessel, over a wide area.

The debris was cleaned up by 45 workers over four days and loaded onto a Marine Department vessel for safe disposal.

A spokesman for the Food and Environmental Hygiene Department said frozen meat carried in sampans thawed fast and could be a source of serious food poisoning.

What happens to the meat and how it is disposed of once it reaches the mainland remains a mystery. One theory is that the consignments are sold in food outlets.