Omiya Ardija president Seigo Watanabe apologized to the J. League on Tuesday over allegations that the Saitama club inflated attendance figures.
"I'm sorry for the trouble we have caused," Watanabe said ahead of a league executive committee meeting. "We want to get to the bottom of things as soon as possible. We will make a statement once our investigation is complete."
Omiya is suspected of padding official attendance for the Oct. 2 Saitama derby against Urawa Reds, which according to the club stood at 33,660.
Saitama Stadium 2002 has a capacity of 63,700. Urawa won 2-1.
The league has ordered Omiya to look into not just the Reds game but other matches for which attendance figures may have been misreported. Hideyuki Hanyu, the league's general secretary, hinted Ardija could face a disciplinary hearing.
"We will wait for their report and see," Hanyu said.