Photo/Illutration Police cars are parked in front of the Sunshine 60 skyscraper in Tokyo’s Ikebukuro district on Oct. 16. (Shoko Mifune)

Investigative sources said members of a loosely organized crime group called the Chinese Dragon were involved in a brawl at a restaurant in a 60-story skyscraper in Tokyo’s Ikebukuro district on the evening of Oct. 16.

The sources said the underworld group had gathered to celebrate one of its members being released from prison.

According to the Sugamo Police Station, a group of around 100 people was dining and drinking at the restaurant on the 58th floor of Sunshine 60 at about 6 p.m. when a fistfight suddenly broke out.

Police officers responding to an emergency call arrived there at about 6:30 p.m.

Most of the group’s members had already left the restaurant by then. One of the few who had remained at the scene was transported to a hospital with a minor head injury.

Investigative sources said they later discovered that the fight involved members of the Chinese Dragon.

The Metropolitan Police Department is currently investigating the incident.

The National Police Agency has categorized the group among quasi-gangs, or an anti-social force under the tier of designated crime syndicates.

Unlike established crime organizations, quasi-gangs are loosely organized and are not covered by the anti-organized crime law.

The Chinese Dragon is believed to be mainly comprised of children and grandchildren of Japanese who were left behind in China amid the turmoil at the end of World War II and returned to Japan decades after the war.