Police have obtained arrest warrants for 12 men and women over a bogus land sale in which homebuilder Sekisui House suffered a loss of about ¥5.5 billion, and took some of them into custody Tuesday, investigative sources said.

The man believed to have masterminded the fraud left Japan for the Philippines last week, they said. The group is suspected of falsifying documents last year to change the ownership of the land in Tokyo's Shinagawa Ward without the owner's permission.

Among those arrested is Masami Haketa, 63, a group member suspected of posing as the female landowner, who was hospitalized in February 2017 and died in June that year, according to police.

Sekisui House had paid some ¥6.3 billion by June 1 last year for a land plot of about 2,000 square meters near JR Gotanda Station, but an application to change ownership was rejected by the Legal Affairs Bureau several days later when the documents were found to have been falsified, according to the company and sources close to the matter.

The land was the site of a closed inn, located some 250 meters southwest of the station, which is in central Tokyo.

Sekisui House booked a special loss of about ¥5.5 billion in its midterm earnings report released in September 2017.

According to a report compiled in January by an external investigation commission, Sekisui House ignored information suggesting the deal was potentially fraudulent and performed inadequate screening as it rushed to acquire the prime-location plot.

In a separate report released in March, the company recognized the responsibilities of its chairman, Toshinori Abe, who was president at the time of the land sale, and Isami Wada, who was chairman, for not understanding the overall deal.