One of two Chinese men arrested on suspicion of attempted fraud paid ¥730,000 for 146 cartons of electronic cigarette cartridges at a Tokyo convenience store using stolen IDs for the new smartphone payment service 7pay, police said Friday.

The police believe an international criminal group, possibly based in China, was behind the operation. They believe the group has been involved in mass-scale ID thefts and online fraud crossing national borders.

Zhang Sheng, 22, and Wang Yunfei, 25, are suspected of using the ID of a man in his 40s in an attempt to purchase 40 of the 146 cartons, worth ¥200,000. They were sent to prosecutors on Friday.

The operator of Seven-Eleven convenience stores on Thursday said some 900 customers using the cashless payment service may have lost a total of ¥55 million after their accounts were hacked.

Wang was responsible for driving the vehicle used by the pair, in which 19 more cartons of e-cigarettes were found. Police suspect e-cigarettes had also been fraudulently obtained by the same means at another store.

The incident came to light soon after the operator, Seven & I Holdings Co., launched the smartphone payment service at over 20,000 outlets nationwide on Monday.

At a Seven-Eleven outlet in Tokyo’s Shinjuku Ward, Zhang used the IDs of seven to eight different people to settle payment for 146 cartons of e-cigarettes, the police said.

The two Chinese men said they had received instructions from a person who had promised them a reward, according to the police.

The police quoted Zhang as saying that he had been participating in a group chat on Chinese messaging app WeChat when someone asked if there was anyone in the group staying in Tokyo’s Ginza district. The person said a reward would be paid to anyone willing to go on a shopping trip.

After Zhang accepted the person’s friend request he received instructions to purchase e-cigarettes, the police said.

Meanwhile, Wang had been told by a relative in China about a part-time job where he could make money quickly, and was put in touch with someone who said it involved “driving a car in Shinjuku.”

The men told investigators that the person who contacted them had the same WeChat alias, the police said.

The police suspect possible involvement of an international group that includes a hacker, a person who gives instructions and others who engage in the purchasing and collection of the merchandise.

The police will also look into how Zhang managed to settle such a large payment at a single outlet.