Superintendent of Police M Tamilvanan said the arrested ultras included Birsa Ganjhu, Ishwar Ganjhu, Jethu Ganjhu, Sainath Ganjhu, Preetam Ganjhu, Naresh Bhuian and Sunil Mandal.
The arrested men had started working as TPC members in the industrial area to collect levy and extortion money from transporters, big contractor and other business establishment in the district, Tamilvanan said.
Inquiries revealed the arrested had recently attacked coal cleaning unit (washery) of Central Coal Fields Limited under Mandu police station of the district and kidnapped 11 workers, who were later released with the threat that no work should be done in coal cleaning unit without their permission, the SP said.