Tokyo police have served two people with additional arrest warrants, including a person believed to be the leader of a group accused of committing phone scam cases, people familiar with the investigation said on Friday.

The Metropolitan Police Department suspects that the group was behind at least some 500 phone scam cases committed in half a year through January, causing about ¥5 billion ($33 million) in damage.

One of the two suspects, who is believed to be the group's leader, is Qian Ling, a 38-year-old Chinese national, who allegedly has a link with a Chinese-affiliated crime organization.