More... bomb was "pressure cooker type" frequently used in Afghanistan... Bombs were loaded with nails and "pellets"... No other bombs found... FBI announces world-wide search for those responsible... Some bomb victims have as many as 40 pellets and nails in their bodies... Pressure cooker device may have been dropped into barrels along race route... Person of interest is Saudi "student," 20-years old, from town near Mecca, living in Revere, being treated for burns... gave police permission to enter his apartment in revere, said to be cooperating with police... not considered a suspect... no one in custody...