The discovery of more than 5 000 donkey hides in a shack and a metal container in Benoni could blow the lid off the illegal slaughter and trade of the animals’ meat and skin, allegedly by a Chinese syndicate.

The find marks the single biggest discovery of donkey hides and a major breakthrough in a case against a syndicate suspected of slaughtering the animals and transporting the meat and hides without them being certified disease-free. The trade in donkey hide, used for medicinal purposes in China, is estimated to be worth millions of rands.

“Two of the individuals that were here claim that it has nothing to do with them, but we believe they may be involved,” said Ashley Ness, an inspector at the Highveld Horse Care Unit.

The bust followed a tip-off from an elderly woman living on a privately owned farm near the suburb of Crystal Park. She could no longer tolerate the putrid smell coming from the shack and sent a picture of what looked like donkey hides piled on a piece of wood to Ness.

The skins, which had been treated with salt, were neatly stacked and hidden behind old furniture and sets of garden tools.

After securing a search warrant, the police’s Cullinan stock theft unit discovered thousands more in a metal container near the shack.

Asked about the source of the hides, the two men gave the police receipts for the purchase of donkeys, which show that at least some of the animals were from villages in Limpopo’s Bochum area, which is about 87km from Polokwane. They bear the stamp of a Bochum headman and indicate the donkeys were sold alive. But the paperwork for thousands of other skins remains unaccounted for.

“The hides will be impounded and, even though we can’t make arrests, the paperwork could assist a great deal,” said Ness.

“Most of the Chinese guys around here disappeared as soon as the Cullinan stock theft unit arrived, because they can’t answer questions about whether they have paperwork to export the skins or veterinary clearance, proving the animals were disease-free,” Ness said.

One of the functions of the Highveld Horse Care Unit is to address cruelty complaints.

No arrests were made at the farm but investigators are hoping that workers there will be able to identify members of the syndicate involved in transporting the hides.

A group of men working less than 300m from the shack where the hides were stockpiled confirmed that the hides were collected regularly by trucks driven by Asian men.

“I have been here since 2012 and started noticing the skin last year,” said James Maluleke. “These skins belong to the Chinese. There is always skin coming in and out of here. A truck comes in and the skin goes into the truck and we never see it again,” he said.

Ness said the hides were inspected for the branding marks of South Africa’s two equine abattoirs and none was found. This rules out the possibility that the animals may have been killed in accordance with the Animal Rights Protection Act.

Christine Kuch, the spokesperson for the National Council for the Societies for the Prevention of Cruelty to Animals (NSPCA), said: “The Meat Safety Act 40 of 2000 allows that a person may slaughter one equine for his/her own consumption every 14 days. This must, however, be done in accordance with the Animal Rights Protection Act. Any meat that is sold for consumption must be slaughtered at a registered abattoir.”

The donkey trade is big business and the demand for donkey hides has spiked in China over the past two years, according to the NSPCA. The gelatin in the hides is apparently used for medical purposes to counter ageing, and treat conditions such as insomnia and poor blood circulation.

“The gelatine is a key ingredient in China’s ejiao [donkey-hide gelatin] industry, which produces tablets, tonics and a sweet syrup. The skins are soaked and stewed to produce or release this substance,” the NSPCA said in a statement.

Tribal authorities in the Northern Cape and Limpopo reportedly sell donkeys for between R200 and R600 each, Ness said, but a donkey hide can sell for up to R7 000. “By the time a 20-foot [6m] container filled to the brim with donkey hides reaches China and is sold on their markets, it is worth approximately R8-million,” she said.

The department of forestry and fisheries, which is assisting a national police unit to track and apprehend the syndicate, said it is gravely concerned about the recent hike in the illegal slaughter and trade of donkeys.

“A task team has been established, working with the South African police at national level, to curb these illegal activities,” said its spokesperson, Bomikazi Malopo.

Arrests for the illegal transportation, theft, slaughter and hide sale have also increased in South Africa since 2015. Last year, four people were sentenced to eight months in prison for animal cruelty after being caught with a truck carrying 41 donkeys from Limpopo to Randfontein.