TALLINN, Estonia (Reuters):

A delegation from Côte d'Ivoire arrived in the central European state of Estonia on Friday as part of the investigation into the deadly discharge of toxic waste in West Africa.

The Panamanian-registered Probo Koala ship was seized on September 27 in the Estonian port of Paldiski on suspicions it was flushing similar waste into the Baltic sea.

Estonia's Environment Ministry has said preliminary tests of the Baltic waters around the vessel have shown disturbing signs.

But Trafigura Beheer, the Dutch-based oil trading firm which had chartered the ship, released a statement saying the fluid on-board the ship in Estonia was dissimilar to the cargo dumped in Côte d'Ivoire (formerly known as Ivory Coast) in August.

"The waste on the Probo Koala in Estonia is not the same waste as discharged in Abidjan," it said in the statement.

Death, suffering

Eight people died and thousands in Abidjan suffered vomiting, stomach pains, nausea, breathing difficulties and nosebleeds caused by pungent fumes from the black sludge discarded at open-air sites after being unloaded from a tanker.

Independent experts say the sludge contained hydrogen sulphide, a chemical which can be deadly in high concentrations.

The firm has described the waste dumped in Africa as "chemical slops", a mixture of gasolene, spent caustic soda and water, and said it was a normal by-product of cleaning tanks used to transport fuel.

Ten people have been charged under the West African state's toxic waste laws and imprisoned in Abidjan. These include two French executives of Trafigura Beheer.

"The delegation from the Côte d'Ivoire arrived today and they have already had a meeting in the prosecutor's office," a spokes-woman from the office said in Tallinn, Estonia's capital, on Friday.

"They discussed what has been happening in Estonia and ex-changed information with the Estonian investigators and the delegations are working out how they can help each other," the spokeswoman said.

She added that the ship remains impounded while the criminal investigation continues.