TOKYO -- The ringleaders in a series of recent burglaries mainly in the greater Japanese capital area used phone numbers with the United States country code when instructing those carrying out the crimes, likely to fake calls from the U.S., sources close to the investigation told the Mainichi Shimbun.

A total of 28 such burglaries and related crimes have been reported in the Tokyo metropolitan area and elsewhere since August, and some 60 people, including those suspected of breaking and entering homes to steal cash and other items, have been arrested.

Police have seized over 100 smartphones from apprehended suspects, with the Metropolitan Police Department's Investigation Support and Analysis Center leading the probe into these devices. Most of the suspects are believed to have received instructions via the highly secure communication app Signal.

According to investigative sources, the smartphones of those carrying out the crimes showed multiple incoming calls from numbers starting with the international code "1," indicating the United States or Canada. The numbers were associated with various area codes spanning states such as Nevada and California.

U.S. phone numbers can be acquired through various internet apps that allow users to choose any area code. By downloading Signal on a smartphone and registering with a U.S.-based phone number, users can make calls with U.S. numbers even if not physically in the country.

Police believe it is unlikely the ringleaders have multiple bases across the vast U.S. territory. Instead, these leaders are thought to have acquired U.S. phone numbers through apps to prevent the discovery of their true locations. Communication with perpetrators was then conducted using Signal accounts linked to these U.S. numbers.

The misuse of international phone numbers has surged in recent years, especially in cases of fraud. According to the National Police Agency, such incidents more than quadrupled from 969 cases in July 2023 to 4,432 in May 2024. Numbers with international codes such as the United Kingdom's 44 and Australia's 61 have also been identified. It is believed that fraud groups began exploiting these international numbers after Japanese IP phone numbers starting with "050" were subjected to identity verification requirements.

In the series of robberies and related incidents, the ringleaders reportedly used at least 30 different accounts, some under aliases using names of historical figures such as "Oda Nobunaga" and "Natsume Soseki," with some overlap between cases. Police suspect multiple ringleaders formed groups to instruct accomplices.

(Japanese original by Ayumu Iwasaki, Kengo Suga and Yuka Asahina, Tokyo City News Department)