A notorious Malaysian wildlife trafficker dubbed the "Lizard King" for his smuggling of endangered reptiles is back in business, according to an Al Jazeera report that prompted outraged wildlife activists Friday to demand action.

Anson Wong was arrested in August 2010 at Kuala Lumpur's international airport while attempting to smuggle 95 endangered boa constrictors to Indonesia.

He was sentenced to five years in jail, but a Malaysian appeals court freed him in 2012, sparking an outcry.

Malaysian authorities had said in the wake of Wong's arrest that his licences for legitimate wildlife trading were revoked.

But, in an investigative report, Al Jazeera said Wong and his wife Cheah Bing Shee were believed to be trading albino pythons and other wildlife from their base in the northern Malaysian state of Penang.

Trade in the pythons requires a permit, said the report by the Qatar-based network, which saw journalist Steve Chao go undercover to talk with wildlife dealers and associates of Wong's.

The report, called "Return of the Lizard King" and aired late Thursday, said documents also revealed shell companies used by Wong to hide his activities.

Illegal trade in wildlife is thought to be worth at least $19 billion a year worldwide, according to conservation groups.

Outraged conservationists demanded action from the government and expressed shock over the lax attitude by the authorities for failing to monitor Wong.

"The 'Return of the Lizard King' raises so many doubts and questions about Malaysia's commitment to that fight. It is time we had some solid answers from government," Shenaaz Khan, an official with wildlife-trade monitoring network Traffic, said in a statement.

Traffic views the revelations about Wong's post-prison activities with deep concern, and seeks a credible explanation on his apparent ability to continue trading wildlife despite government promises to the contrary, she said.

In Penang, Al Jazeera's Chao confronted Wong on camera, but he declined to comment.

Several of Wong's former associates also claimed that corrupt customs officials in Malaysia, Indonesia and Madagascar were helping to facilitate Wong's activities, the report said.

In a press release, Al Jazeera said Chao and his team worked with anti-trafficking groups to track Wong's Malaysian-based operation.

Kadir Hashim, enforcement director of Malaysia's wildlife department, confirmed Wong's permits remained revoked.

"The department is investigating both" Wong and Cheah, he said in an e-mail response to an AFP inquiry, without elaborating further.

Wong is described by wildlife groups as one of the world's most active smugglers of wild animals.

He was sentenced to 71 months in jail in the United States in 2001 after pleading guilty to trafficking in endangered reptiles.

Despite efforts by Southeast Asian authorities to crack down on animal smuggling, the practice persists and poses a threat to a number of threatened species, conservationists say.