Three Algerians who are considered close to a suspected ringleader of the Madrid train bombings are being questioned about an alleged plot to kill judges investigating Islamic terrorists, officials said Thursday. The three are among 10 prisoners who have been isolated from other inmates for questioning over a possible link to the alleged plot targeting the National Court with a suicide truck bomb packing 1,100 pounds of explosives, police said. In 2001, the court convicted the three of belonging to an Algerian terrorist group along with Allekema Lamari, who was released from jail in 2002 in what officials said was an administrative mistake. Lamari is now suspected of having been a ringleader of the March 11 train bombings in Madrid, which killed 191 people.Lamari has been identified as being among seven suspects who blew themselves up April 3 as police investigating the bombings prepared to arrest them in an apartment outside Madrid. A police spokesman declined to comment on Lamari's relationship with the three isolated inmates. But the newspaper La Vanguardia quoted one investigator as saying: "It is not that the three knew Lamari. Rather, they were his people." The alleged leader of the court bombing plot, Mohamed Achraf, is said to have recruited cell members while jailed in Spain for credit-card fraud. Eight suspected cell members were arrested in Spain this week on the basis of testimony from an informant who was in contact with Achraf. One of those eight detainees, Madjid Sahouane, was arrested in Spain in September 2001 on suspicion of links to terror suspects elsewhere in Europe, but a judge freed him on bail a month later and threw out the case in February of this year, citing lack of evidence.