The forest department is trying to track down members of the international racket allegedly behind the smuggling of the lion cub and three langurs that were rescued on Saturday.

Officials said members of the racket would call each other through the Voice Over Internet Protocol (VoIP) to avoid detection. VoIP allows people to make calls using broadband Internet.

The three-month-old Asiatic lion cub and three langurs — one Javan and two White Headed — were found trapped in nylon bags stitched on both sides in a Mahindra Scorpio.

The car was intercepted on Belghoria Expressway near Kendriya Vihar Housing Complex in Dakshineswar around 2am on Saturday.

Three men in the car — garments trader Wasim Rahman, 29, aluminium trader Wajid Ali, 36, and Mohammed Ghulam Gaus, 27 — were arrested.

A Barrackpore court released them on bail on Saturday.

“The registration number of the white Mahindra Scorpio is fake,” the forest department official said. “The number belongs to a Yamaha RayZ scooty registered in Howrah. We will speak to the owner of the two-wheeler.”

The department has sought the call detail records of the cellphones of the accused. “We are tracking the numbers the men would call or send messages to frequently. Almost all the numbers have gone off the grid,” the official said.

The accused have apparently told forest department officials during questioning that they had smuggled wild animals on least two occasions before. They had allegedly brought the animals from Thailand to Myanmar by road and from there to Bangladesh.

For the latest consignment, they said, they had been paid more than Rs 50,000.

The animals rescued on Saturday were all sedated. “They were being smuggled through the Benapole-Petrapole border and were on their way to a private zoo at a farmhouse in western India,” another official in the forest department said.

The department has picked up signs of a growing trend of rich businessmen and owners of large estates keeping wild animals on their premises.

“The trade is fuelled by the rivalry over who has the maximum number of exotic animals or animals belonging to endangered species,” the official said.

The officials who were tracking the men arrested on Saturday spent at least seven days on the Indian side of the India-Bangladesh border near Bongaon, in North 24-Parganas. An official of the Wildlife Crime Control Bureau, who was part of the team that was camping near the border, said they had spent several nights under plastic sheets at a burning ghat.

“Smugglers have their contacts in hotels and guest houses along the border. Information about us would have reached them had we checked into a hotel or guest house,” the officer said.

Arkaprava Bhar, a member of the Animal Welfare Board of India, said the lion cub alone would have cost a fortune. “Clearly, the animals had been ordered by someone with very deep pockets.”