The ship, the Probo Koala, was a Panama-registered tanker chartered to the Dutch company Trafigura. Before it dumped the waste in Abidjan, it attempted to have the waste processed in Amsterdam, Netherlands, but Amsterdam Port Services BV, the company that had contracted to take the waste, refused after its staff reported an incredible smell coming from the waste. A company specialized in the disposal of chemical waste, Afvalstoffen Terminal Moerdijk tendered the disposal of the waste (based on the samples it received) for 500,000 Euro. The Proba Koala then left for Côte d'Ivoire where "Compaigne Tommy", which was registered only days before the arrival of the Probo Koala, was contracted for 18,500 dollars to dispose of the waste.
A Dutch newspaper reported that the waste could have been generated as a result of attempted on-board desulfurization (removing mercaptans) of naphtha in a Merox-like process. In this way high mercaptan laden gasoline is upgraded to meet certain country specific specifications. This would explain the water/caustic soda/gasoline mix and also the presence in trace amounts of a certain catalyst called ARI-100 EXL, generally used in this process. It would on the other hand not explain the presence of hydrogen sulphide because the final stage of the Merox process is the disulfide unless the attempt at desulfurization had failed.
On 11 November 2006, a GBP100 Million lawsuit was filed in the High Court in London by the UK firm Leigh Day & Co. alleging that "Trafigura were negligent and that this, and the nuisance resulting from their actions, caused the injuries to the local citizens. Martyn Day, of Leigh Day & Co said, "This has been a disaster on a monumental scale. We hold Trafigura fully to account for all the deaths and injuries that have resulted from the dumping of their waste." In response, Trafigura announced on Monday 13 November 2006 that it has started libel proceedings against British lawyer Martyn Day, of Leigh Day & Co.
Shortly after it became apparent that the toxic slops from the Probo Koala had led to the outbreak of sickness, two Trafigura executives, Claude Dauphin and Jean-Pierre Valentini, travelled to Abidjan to offer their help. They were arrested on 18 September, four days after their arrival, and have been held in Abidjan's Maca prison since. There have been several reported attacks of the two executives. Trafigura has called for the immediate release of Mr. Dauphin and Mr. Valentini.
On December 6 2006 an independent inquiry launched by the city of Amsterdam concluded that the city was negligent when they allowed Trafigura to take waste back on board the Probo Koala in Amsterdam in July. Part of the Probo cargo was offloaded with the intent to have it processed with an Amsterdam waste processing company but when this turned out too expensive Trafigura took it back. The responsible local civil servants were unaware of existing Dutch environmental laws that would not allow its export given these circumstances. On December 19 2006, a majority of the Dutch Second Chamber expressed their desire for a new investigation into the Probo Koala. On January 8, 2007, the Guardian reported that the legal team for Leigh Day had arrived in Abidjan, and would begin taking statements from thousands of witnesses in the area.
On February 13 2007, the Dutch-based oil trading group Trafigura agreed to pay the Ivorian government US$198m for the clean-up of the waste; however the group denies any liability for the spill and as a part of the deal the government will not pursue further action against the group.The Trafigura employees Claude Dauphin, Jean-Pierre Valentini and Nzi Kablan, held by the Ivory Coast authorities after the incident, would now be released according to Trafigura.
On May 18 2007, The Dutch newspaper Volkskrant reported that the press officer of Trafigura, (operating under the username Press Office T NL), tried to alter the Dutch Wikipedia article of the Probo Koala on three separate occasions, with intent to clear their name. The page is now locked and is not accessible for modifications.