The claim that traces of the deadly poison ricin had been found in the London apartment of alleged al-Qaida operatives, first broadcast...

WASHINGTON — The claim that traces of the deadly poison ricin had been found in the London apartment of alleged al-Qaida operatives, first broadcast around the world in early January 2003, has been proved wrong, a senior British official said yesterday.

At the time, authorities said the apartment housed a terrorist “poison cell,” based principally on the discovery of a mortar and pestle bearing traces of what was identified as ricin. Authorities also found 22 castor beans, whose seeds contain ricin, and notes in Arabic with a formula for ricin.

Wednesday, however, evidence that ricin was not on the mortar and pestle surfaced after the end of the London trial, conducted under British secrecy law, of five people who had been arrested in connection with the Jan. 5, 2003, raid on the apartment.

Evidence introduced during the trial included a document from a senior British scientist saying tests showed that “the material from the pestle and mortar did not detect the presence of ricin,” according to George Smith, a scientist and senior fellow at GlobalSecurity.org.

Yesterday, it was disclosed that the only person convicted of poison conspiracy was Kamel Bourgass, 31, an Algerian who had lived in the apartment. Four others were cleared of conspiracy.