Police have arrested 75 people in a crackdown against a faction of a triad society in Tuen Mun monopolising the decolouration of marked oil and the sales of illicit fuel in Nai Wai Village.

The operation, codenamed "Buttonhead", started on May 8. The syndicate's 46-year-old mastermind and three two-way permit holders were arrested.

Among the 72 men and three women arrested, 40 men and the three women have been released on Police bail pending further investigation. A total of 13 oil tankers and 22 other vehicles were also seized.

More than 300 police officers from the Crime New Territories North Regional Headquarters, Traffic New Territories North, Tuen Mun District and Police Tactical Unit, and about 100 Customs officers took part in the operation.

They raided the de-treatment plant in Nai Wai Village and 11 sales outlets. They found seven tanks in the de-treatment plant containing 20,000 litres of illicit fuel.

The operation is continuing.