They were the first suspects taken into custody since the case was revealed by The Associated Press in a report two months ago.
The arrests were made yesterday and late Friday in the remote island village of Benjina, said Lt Col Arie Dharmanto, National Police anti-trafficking unit chief.
Five Thai boat captains and two Indonesian employees at Pusaka Benjina Resources, one of the largest fishing firms in eastern Indonesia, were taken into custody.
The arrests come after the AP reported on slave-caught seafood shipped from Benjina to Thailand, where it can be exported and enter the supply chains of some of America's biggest food retailers.
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Police will recommend they be charged by prosecutors. If the men go to trial, they could face jail sentences of up to 15 years and fines as high as USD 46,000, he said.
He said the number of suspects would likely climb because authorities are still investigating how thousands of foreign fishermen from Myanmar, Cambodia, Laos and Thailand were put on fishing boats in Thailand sometimes after being tricked or kidnapped and brought to work in Indonesian waters where they were not allowed to leave.
The AP investigation found that tainted fish can wind up in the supply chains of some of America's biggest food sellers, such as Wal-Mart, Sysco and Kroger.
It can also find its way into the supply chains of some of the most popular brands of canned pet food, including Fancy Feast, Meow Mix and Iams.
The companies have all said they strongly condemn labor abuse and are taking steps to prevent it, such as working with human rights groups to hold subcontractors accountable.