Three people were arrested in Seville and a fourth investigated in Murcia after officers intercepted a container at the port of Algeciras holding 19 tonnes of vehicle engines, fuel tanks with gasoline residue and other oil-soaked waste, the regional government of Andalusia said.

"The customs paperwork did not match the container's contents, indicating alleged document falsification and possible customs fraud," it said in a statement.

International rules ban sending hazardous waste to countries without proper treatment facilities.

The suspects, all Ghanaian nationals, face charges including environmental crimes and belonging to a criminal group.

Environmental watchdogs and Interpol have long warned that European countries are a major source of hazardous shipments disguised as second-hand goods.

The lucrative trade exploits weaker enforcement in receiving countries and the high cost of proper recycling in Europe, turning parts of Africa into dumping grounds for the world's unwanted electronics, machinery and industrial refuse.