JIANGSU PROVINCE, CHINA — Chinese police arrested 13 people accused of managing a ring of 13 porn websites that served as many as 12 million registered members, officials reported Thursday. Six computers, 25 bank cards and a car were seized.The websites, hosted on 14 servers in the U.S., were shut down on Wednesday. According to the official Xinhua News Agency, the ring was one of three major providers of pornography that “poisoned Chinese netizens.” The sites, one of which was named “Heaven of the Lost Girl,” offered explicit content featuring Chinese women.

Until Wednesday, police had been stymied in their attempts to uncover the operation’s ringleader. Identified only by his surname, Shen, the man was careful to hide his tracks and obscure personally identifiable information connected with the sites’ ownership.

Eventually, a banking misstep tripped him up. According to police, website members deposited fees into two anonymous online accounts at ICBC. Shen accessed the accounts via foreign servers to manage the money, but when he needed to withdraw funds, he did so via ATMs in three Chinese provinces. Since the first of this year, Shen had withdrawn more than 300,000 yuan (about U.S. $44,000) from the accounts, police said. A single slip in covering his tracks — committed in January when Shen accessed the bank accounts using an IP address police traced to a Beijing address — led to Shen’s unmasking.

According to officials, Shen set up the porn ring in 2007, hired more than 300 people to manage them, and collected more than 750,000 yuan from members over the course of the sites’ existence.