The MV Republica Argentina arrived at Lagos' Roro terminal from Hamburg on Thursday and was met by customs officials as it unloaded a Mercedes Benz truck packed with a mystery substance, Monic Ohaka said.

"The truck was being offloaded when it was discovered to contain substances strongly suspected to be toxic waste," she said.

The port area was enveloped with an "offensive odour" as soon as the truck was opened, she said.

Nigerian officials suspect the substance may be dangerous and a sample has been taken for laboratory analysis, she added.

The vessel has since returned to Germany with its consignment, Ohaka said, appealing to importers to stop bringing in dangerous substances.

Nigeria has complained in the past about attempts by European firms to illegally ship hazardous chemicals to the west African country.

In 1988 an Italian firm dumped toxic waste on a beach near the town of Koko in the southern Niger Delta region, sparking a diplomatic row when the Nigerians seized an Italian ship and forced it to take the barrels back.

TERRA.WIRE