Authorities announced another arrest in the Madrid terror bombings Monday and sent police to patrol subway and bus stations

Authorities announced another arrest in the Madrid terror bombings Monday and sent police to patrol subway and bus stations, as a newspaper said a group linked to al-Qaida threatened to turn Spain into "an inferno." Court officials said the arrest came Saturday in Ceuta, a Spanish enclave on the Moroccan coast. No details were given on the man's identity or possible role in the March 11 train attacks, which killed 191 people. Another suspect whose weekend arrest was also announced Monday has been released after questioning, officials said. The arrest raises to 16 the number of people in custody, including six charged with mass murder. Interior Minister Angel Acebes confirmed Monday that one of those killed in a suicide blast Saturday in an apartment south of Madrid was Moroccan Jamal Ahmidan, a prime suspect in the bombings. At least five terror suspects are believed to have died in the explosion, along with a special forces officer. One of the suspected terrorists has yet to be identified. Sarhane Ben Abdelmajid Fakhet, a Tunisian believed to be the overall leader of the attacks, was among those killed, Acebes said. A U.S. intelligence official said people should not think that the terrorist threat in Spain is over because of the arrests and deaths of the suspects in the train bombing.