At least seven Japanese nationals have been taken into protective custody from large-scale scam centers at the Thai-Myanmar border — thought to hold at least 120,000 people — with many more still believed to be in captivity.

The Japanese nationals are among hundreds of thousands of people who police say have been coerced into engaging in online scams. On Thursday, authorities in Thailand began to send back those that had been held at the scam centers in large numbers, with 200 Chinese citizens sent back to their country and hundreds more expected to be in the coming days.

Keiichi Iwamoto, a senior Foreign Ministry official in charge of consular affairs, said Thursday in parliament that two boys — high school students age 16 and 17 — along with five other Japanese nationals had been taken into custody in Thailand. Six of them have already returned to Japan.

Four had been detained by the Thai police earlier this month for illegally crossing the border into Myanmar.

“Due to the political unrest in Myanmar, it is difficult to gauge the situation through local authorities, and therefore as the national police, we are working to understand the situation through investigations of those involved,” Shigeyuki Tani, the National Police Agency’s director of the criminal affairs bureau, said on Thursday.

“We believe that the scam center may be used as a base for fraud against people in Japan and that there may be other Japanese nationals still held there,” he added.

A Foreign Ministry official said that although there are many numbers floating around in the media, they are as yet unsure how many people may still be held captive in the area and are continuing efforts to get a handle on the situation.

If more are detained, they would most likely be sent back to Japan in cooperation with Thai authorities under standard protocol for when a Japanese national is detained abroad, the official said.

Given that one of the high school students rescued had been encouraged to fly to Thailand for a job by a person he met socially through an online game, the NPA said that there is a high likelihood that Japanese people may also be involved in the operation of the crime syndicate thought to be running the scam centers.

According to reports by NHK, the 17-year-old student from Miyagi Prefecture said that he was forced to scam Japanese people with the assistance of a 29-year-old Japanese man — who was arrested by Thai police earlier this month and was allegedly responsible for bringing the boy to Myanmar — under orders from a Chinese man.

The student said the criminal organization threatened to seek retaliation if he spoke to the police, Jiji Press reported.

Among the four that had been detained in Thailand, one of them has been arrested by Ibaraki police for using cocaine, based on a warrant issued before he departed the country, it was reported Thursday.

He is set to be investigated over his involvement in criminal operations in Myanmar, with the other three expected to be questioned.

The Thai Royal Police is cracking down on the issue, having held a meeting on Thursday to implement a four-step action plan for immediate enforcement, including intensified screenings of foreign nationals entering the country and conducting field inspections of those residing in Thailand.

They also warned that corrupt police officers aiding the crime syndicates would face strict disciplinary measures.