Hong Kong customs seized HK$4.3 million (US$552,000) worth of smuggled diesel oil and goods vehicles at two border control points as part of a special operation last month, the agency revealed on Thursday.

Eight male drivers, aged between 31 and 53, were arrested during the operation which ran between January 12 and January 31.

Customs officers intercepted seven vehicles at the Lok Ma Chau border crossing and one at Shenzhen Bay Control Point. The eight trucks and 9,700 litres of suspected smuggled diesel oil were confiscated.

Each vehicle had installed a fuel tank with a suspected altered structure to carry the oil.

Hong Kong customs seized a total of 9,700 litres of suspected smuggled diesel oil and eight goods vehicles.

According to the Customs and Excise Department, all eight suspects have been released on bail, pending further investigation.

“During the operation, officers stepped up inspections of outbound goods vehicles at land boundary control points through risk-management and intelligence-based enforcement strategies,” the department said in a statement.

Hong Kong is known for its expensive fuel prices, with diesel costing US$2.33 per litre, more than double the worldwide average of US$1.14 per litre as of January 31, according to research institute GlobalPetrolPrices.com.

The city’s maximum penalty for importing or exporting unmanifested goods is seven years in jail and a HK$2 million fine.

Last year, customs officers seized more than HK$1.1 million worth of smuggled diesel oil in 42 cases, and arrested 160 people.

In 2019, the department confiscated diesel oil with a total value of HK$882,000 over 31 cases, and arrested 63 people.