A group of 15 suspected Japanese scammers arrested last week in Thailand acquired more than ¥225 million ($2 million) in illegal proceeds in February and March alone, Thai police and other sources said Tuesday.

Records seized in a March 30 police raid on a rented upscale house in the seaside resort town of Pattaya show that the suspects scammed victims in Japan of some ¥136.86 million between Feb. 1 and 24, and another ¥89 million during March.

The records show the highest value of what was described as “sales” in any one day in February was ¥14.04 million and the lowest was ¥2.74 million.

Thai and Japanese police continue to examine the records in an attempt to grasp the extent of fraudulent activities and to clarify details regarding the gang, whose members have been charged with working illegally in the kingdom.

At a news conference in Bangkok, the police also released a “fraud manual” seized during the raid, in which they also seized 52 internet protocol phones, 19 notebook computers, routers and other equipment as well as a list of victims and bank accounts.

In the printed A4 sheets it is clearly stated that in one scam, victims were to be told that “(as) the charges for the paid site are unpaid, the civil trial is progressing.”

Earlier, police had said that the scammers particularly targeted people in Japan who are retired and living alone, falsely claiming that their phone use exceeded a limit and that they would need to pay an excess charge to continue using their phones.

After being arrested, the 15 suspects, all men aged between 22 and 54, were transferred to an Immigration Bureau holding center in Bangkok. They were interrogated earlier Tuesday.

At the news conference, they were all were dressed in orange T-shirts and remained silent, wearing masks and facing away from the press to avoid the cameras.

Besides those in detention, the police suspect that as many as four more Japanese and Thais were involved in fraud scheme.

Japan’s National Police Agency personnel are expected to go to Bangkok later this month to proceed with investigations.

According to the police, it is the first time such a scam victimizing people in Japan has been uncovered in Thailand. The gang is believed to have used the country as a base because Japanese nationals can enter without a visa and it offers easy, high-speed internet access.