Spain was plunged into further terror crisis today when a bomb was discovered on a high speed rail line near Madrid that was being used by hundreds of people heading on holiday.

The army was drafted in to guard rail lines after it was discovered that the explosives might be the same kind used in the March 11 terror bombings that killed 191 people on trains in the capital.

Interior Minister Angel Acebes said initial analysis of the 26 pound bomb – found on a line between Madrid and Seville ? suggested it might be a Spanish brand of dynamite called Goma 2 Eco ? the explosive used in the March 11 backpack bombs.

“Because of its colour and texture,” Acebes told a news conference, “it might be Goma 2 Eco.”

He added: “Now it is going to be analysed but the specialists say it might be Goma 2 Eco.”

Bomb-disposal experts alerted by a railway employee found the bomb under a track about 40 miles south of Madrid.

The state railway said no train was close to the bomb when it was detected.

The explosives were connected to a detonator with a 136 yard cable, the minister said.

Acebes said the bomb failed to go off because it did not have a trigger – suggesting that the bomber or bombers may have been scared away by security guards as they were planting the device.

He said it was not immediately known who placed the bomb.

“As we get information regarding those possibly responsible or details that move the investigation forward, we will give them to you,” Acebes added.

The train bombs last month were detonated remotely by mobile phone.

Friday was a busy travel day in Spain, with trains and roads packed people leaving home for the Easter holidays.

Judge Teresa Palacio, the investigating magistrate on duty at the National Court, said there was no evidence that would point to either the armed Basque group Eta or al-Qaida in the failed attack.

Eta has in the past targeted Spanish rail lines but if the explosive is the same as the Madrid bombings suspicion would fall on al-Qaida linked terrorists.

The targeted line serves mainly Spain’s AVE high-speed trains, which have a maximum speed of 190 mph.

The discovery of the bomb came less than a month after 10 backpack bombs ripped through four commuter trains in Madrid, killing 191 people and injuring more than 1,800.

The focus of that investigation is a Moroccan extremist group with links to al-Qaida. The bombs were detonated with mobile phones attached to the explosives.

Interpol has issued wanted notices for six men suspected of involvement in the Madrid attacks.

The wanted notices follow an international arrest warrant issued by Spanish authorities for the six.

“As always in such cases, the wider the net is cast for fugitives, the more chance there is that they will be apprehended,” said Interpol head Ronald Noble.

According to the Spanish warrant, a 35-year-old Tunisian, Sarhane Ben Abdelmajid Fakhet, led the group. He allegedly helped arrange the rent of house outside Madrid where investigators say the bombs were assembled for the March 11 attacks.

The five others named in the Spanish warrants were identified as Moroccans: Jamal Ahmidan, alias El Chino Said Berraj Abdennabi Kounjaa, alias Abdallah Mohammed Oulad Akcha, and his brother Rachid Oulad Akcha.

On Thursday, police in northern Spain defused three letter bombs addressed to journalists in Madrid.