A bomb was found Friday on a high-speed line between Madrid and Seville just three weeks after 191 people were killed in attacks on four Spanish commuter trains, officials said.
But reports that the device was similar to the explosives used in the March 11 bombings blamed on Islamic militants which also left 1,900 people injured were not immediately confirmed.
The Madrid train bombings sparked an outpouring of anger across Europe and forced governments onto the offensive, with EU leaders agreeing in emergency talks a series of measures to step up the fight against terrorism.
Spanish Interior Minister Angel Acebes announced the discovery of the new bomb on Friday, saying police were immediately alerted after a sack was found containing some 10 kilograms (22 pounds) of explosive and linked by a 136-metre (450-foot) cable to a detonator.