Police raided yesterday an apartment in Halandri, northeastern Athens, that they believe was used by suspected members of the Conspiracy of the Cells of Fire urban guerrilla group, which engaged in a letter bomb campaign last month. Officers said that the property had been empty since the beginning of November. They believe that it was used by Gerasimos Tsakalos and Panayiotis Argyriou, who were both arrested on November 1 on suspicion of having used Athens courier firms to send dozens of letter bombs, some of which were addressed to European leaders such as German Chancellor Angela Merkel and French President Nicolas Sarkozy. Thirteen people have been indicted to stand trial in connection to the bloodless activities of Conspiracy of the Cells of Fire, which began its bombings in 2009. The first suspected members of the group were arrested following a raid on another property in Halandri last year.