In early 2002, the Metropolitan Police made a number of arrests in regards to the Wood Green ricin plot, an alleged Islamist bioterrorism plot using the poison ricin (derived from seeds of the castor oil plant) by immigrants of Algerian-origin against the London Underground. Later the same month, during a raid on a flat in Crumpsall, north Manchester, DC Stephen Oake was murdered with a kitchen knife by Kamel Bourgass, an illegal immigrant from Algeria. Bourgass also stabbed three other members of Greater Manchester Police. He was wanted in connection to the Wood Green ricin plot, but was not immediately recognised. Bourgass had attended meetings of "Al-Muhajiroun" leading up to the incident and in the aftermath, six days later Finsbury Park Mosque was raided. The nature of the plot itself was controversial, no purified ricin was found, though notes and castor oil seeds were and most of the people arrested were eventually released. The only person ultimately convicted in court in 2005 in relation to the ricin plot was Bourgass, this was largely due to having notes in his possession on how to make ricin, cyanide and botulinum. Nevertheless, Colin Powell in his February 2003 presentation to the United Nations, arguing for commissioning the Iraq War based on alleged connections between Saddam Hussein and "al-Qaeda", made reference to a "UK Poison Cell" as part of an international network.