Human rights group cast a doubting eye over Thailand’s statement on wrapping up the nation’s largest investigation into human trafficking.

On Tuesday, the Thailand police force said they had “shown sincerity” and called the investigation off, but rights groups raise questions as stones are still left unturned, Reuters reported.

The rights groups, including the New York-based Human Rights Watch, has said the investigation would not put an end to networks operating in the region.

Thailand researcher at Human Rights Watch, Sunai Phasuk, told Reuters that it was possible for the investigation to be a decoy for Thailand facing international pressure.

"It will just put them under ground for the time being and then resurface again,” Sunai said.

Following the sighting of more than 300 corpses buried in the southern camps, Thailand embarked on a manhunt to shut down the trafficking networks in its mountainous areas.

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Police deputy commissioner-general, Aek Angsananont called the investigation "the biggest human trafficking investigation in Thailand's history".

"This government has shown its sincerity in solving this problem by seriously tackling human trafficking and by dealing with those involved," Aek said.

About 1,000 police personnel have been deployed largely in southern Thailand for the investigation to clamp down the perpetrators.

Aek also said that the police have submitted 19 cases which are filled with over 100,000 document sheets to the Office of the Attorney General to which they have July 24 to make a decision to take charges.

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56 suspects among others including politicians, government officials, businessmen and army general have been apprehended and 63 arrest warrants have been issued.

Last month in Malaysia, 139 grave yards were found in jungle camps utilized by suspected smugglers and traffickers and some 12 officers are under investigations.