Japanese police will launch an investigation into a major phone scam based out of Thailand in which hundreds of people across Japan are believed to have been swindled out of more than ¥200 million ($1.8 million) this year, investigative sources said Wednesday.

Following the arrest late last month of 15 suspected Japanese scammers by Thai police, Japan has decided to dispatch investigators to Thailand next week to better grasp the whole picture, the sources said.

The men, their ages ranging from their 20s to their 50s, are suspected of targeting people in Japan, particularly those retired and living alone, from a rented luxury house in the seaside resort town of Pattaya.

On Wednesday, Thai investigative authorities revealed one of the likely victims was a woman in her 50s who lives in Fukui Prefecture.

She purchased electronic money on March 29 in line with the scamming group's instructions and seems to have been swindled out of several hundred thousand yen, according to the police.

Japanese police plan to arrest the 15 suspects after they are expelled from Thailand. They may also build a case against the group over a separate case of alleged fraud.

Other than the 15, Thai police suspect three to four more Japanese and Thais may have been involved in the scam.