(CNN) For more than five years, mutilated bear carcasses appeared all over the central Indian state of Madhya Pradesh . Many were missing their genitals and gall bladders.

To solve the mystery, the state's Forest Department set up a special task force. Ritesh Sarothiya, head of the task force's wildlife division, told CNN that its agents had a suspect in mind: in 2014, a man had been arrested for poaching sloth bears and tigers. After spending a year in jail, he skipped bail and slipped under the radar.

The agents also had a theory as to why the bears were missing some of their body parts. Bear gall bladders are a source of bile, a fluid secreted by the liver and used in traditional medicines across Asia.

Ursodeoxycholic acid, one of its main components, has been medically proven to help dissolve gallstones and treat liver disease. But its other uses lack scientific evidence.

Most Asian countries have laws prohibiting domestic sales, and the international trade of bear products is prohibited under the Convention on International Trade in Endangered Species ( CITES ). Yet the market is enormous, and thousands of bears remain trapped in bile farms across Asia, where they're kept alive so the fluid can be regularly extracted to meet consumer demand.

Poachers look to India

Asiatic black bears are the preferred source of gall bladders. They're listed as vulnerable under IUCN's Red List of Threatened Species -- as are sloth bears, which are also protected by India's Wildlife Protection Act.

Also known as moon bears due to the cream-colored crescent on their chest, Asiatic black bears have traditionally been poached in the wild in Southeast Asian countries like Vietnam, Cambodia, Laos, Myanmar, Indonesia and Malaysia. Due to overhunting their populations have declined dramatically in those countries, according to wildlife conservation NGOs.

This has led to a rise in poaching in countries like India. Out of 694 bear-related seizures reported in Asia between 2000 and 2011, only 23 involved India -- as opposed to 190 involving Cambodia, 145 involving China and 102 involving Vietnam, according to an investigation by conservation NGO Traffic.

Workers prepare to move a moon bear rescued from a bear bile farm in Chengdu on February 6, 2009.

But India's share of the market is growing fast. "It is a classic phenomenon: as a species go down in one country, poaching moves to another one where it is still abundant," says Lalita Gomez, a wildlife trafficking expert based in Malaysia, who describes the poaching of sloth bears in India as "rampant".

The hunting of bears in India has also been bolstered by a reduced supply of bile from Asia's bear farms, as more and more countries move away from the controversial practice.

"In the past couple of years, Vietnam has been actively shuttering these operations," says Jill Robinson, the founder of Animals Asia, a Hong Kong-based NGO fighting to save Asian black bears.

"There are only about 600 farm bears left in the country, compared to 4,000 a few years ago."

Production is also shrinking in South Korea, Cambodia, Laos and -- to a lesser extent -- China, due to international pressure. A research paper published in 2018 identified just seven facilities in Laos holding about 116 Asian black bears.

The decline in competition from other suppliers creates an incentive for poachers elsewhere to cash in.

Laying traps

On October 19, Madhya Pradesh's special task force tracked down their suspect to a hut next to a highway in the state of Gujarat. The 30-year-old man, who goes under several aliases including Yarlen, had three fake IDs on him.

After his arrest, Sarothiya said Yarlen admitted he had been a poacher for nearly a decade and had killed numerous tigers, sloth bears and other wildlife, including a tigress called T13 whose skin was found in Nepal close to the China border in 2013.

Yarlen, one of India's most wanted wildlife traffickers, was arrested on October 19 after several years on the run. He admitted to killing a number of sloth bears and tigers.

He would lay traps near water bodies. Once his prey was ensnared, he would beat it to death with sticks, Sarothiya said.

The poached animals were sold to international trafficking syndicates. "He killed the sloth bears and tigers to sell certain body parts that are in high demand, mainly in China and southeast Asia, such as the gall bladder and genitals," Sarothiya alleged.

The man, who belongs to the nomadic Pardhi tribe, is being investigated for several cases of poaching and trading of endangered wild animals. He is expected to be charged under violations of the Wildfire Protection Act and could be imprisoned for up to seven years.

Until his arrest, he had been one of India's most wanted wildlife traffickers.

"He had five different cases against him so he was definitely a big one for us," Sarothiya said.

Ancient practices

Traditional Chinese Medicine (TCM) is the main driver for the trade in bear bile. The gold-colored liquid has been used in traditional medicine in China for thousands of years, with the first reference appearing in a Tang Dynasty medical text in 659 A.D. It is prescribed for epilepsy, hemorrhoids, heart disease, cancers, colds and hangovers.

It has been produced synthetically since the 1950s, but believers in traditional medicine prefer to use the natural form.

Once a bear is poached, its gall bladder is extracted and milked for bile, which is then transformed into pills, vials and creams. There are production facilities in Japan, Malaysia, Myanmar and Vietnam, according to a report by Traffic -- however most are in China, with an analysis of 409 bear product seizures between 2000 and 2010 showing that 98% originated there.

Bear bile products are then re-exported illegally and sold all over Asia. This trade is forbidden in most Asian countries, except in China and Japan, where domestic sales of bear bile remain legal.

Bear bile products for sale in Malaysia, identified by wildlife NGO Traffic. The gall bladder (on the left) was found in a shop in Selangor, whereas the vial of pure bile (on the right) was allegedly imported from China.

Traffic found bear bile items in 12 Asian countries or territories, according to its report. Products were most frequently observed in China, Hong Kong, Malaysia, Myanmar and Vietnam, it said.

Prices for whole gall bladders were as low as $51.11 in Myanmar and as high as $2,000 in Hong Kong. "Demand is strong anywhere with a large ethnic Chinese community," says Lalita Gomez.

Wild bear poaching accounts for only a fraction of the bile sold worldwide.

Painful extraction

Large amounts also come from farmed animals. Vietnam, South Korea, Cambodia, Laos and China all operate bear farms, according to Animals Asia. They are illegal in all of these countries except China, which remains the largest producer of farmed bile with more than 10,000 bears held in captivity, it adds.

This photo taken on August 14, 2018 shows a caged bear during a rescue operation from a facility where bear bile is extracted in Thai Nguyen province, in Vietnam.

The conditions in which the bears are held captive and the bile is extracted have been widely criticized by conservation NGOs. "They are given the drug ketamine as an anesthetic, which means they are fully aware of what is happening but just can't move," says Robinson from Animals Asia. "The gall bladder is probed with a needle and a mechanical pump is used to extract the bile, which causes tremendous pain to the animals."

In some cases, bears undergo surgery to create a permanently open duct from the gall bladder to the abdomen, from which bile drips freely, causing infections and abscesses, according to Animals Asia

But even though bear farms were introduced in the 1980s to take the pressure off poaching, wildlife traffickers like Yarlen are not about to go out of business. Many consumers prefer bile from wild bears, believing it to be more potent and purer.

"Once customers have tried farmed bile, they often go on to wanting the real thing," says Robinson.