Fourteen suspected Islamic militants detained on suspicion of planning a terror attack in Barcelona have been transferred to Madrid for questioning at the National Court, officials said Sunday.

Investigators were painstakingly sifting through evidence uncovered during Saturday's arrests, which were triggered by reports from several European intelligence agencies, an Interior Ministry spokesman said.

Police made the arrests as they searched five homes in the area, seizing three large bags containing four timers and substances that could have been used to make bombs, the spokesman said on condition of anonymity in keeping with government rules.

On Saturday, Interior Minister Alfredo Perez Rubalcaba said more arrests were expected and the country was on high security alert.

"When someone has timers at home you have no option but to think violent acts are being planned," he said.

Civil Guard officers made the arrests as part of raids planned with the National Intelligence Center, the Spanish equivalent of the CIA, Rubalcaba said. Five homes were searched he said.

Prime Minister Jose Luis Rodriguez Zapatero confirmed the arrests and said investigations were continuing.

Europe's worst Islamic-linked terror attack took place in Spain on March 11, 2004, when bombs went off in railway carriages during the morning rush hour near Madrid's Atocha station. The attack killed 191 people injured more than 1,800. Twenty-one people have been convicted of involvement in that attack.

Since the Sept. 11, 2001, attacks in New York and Washington, Spanish police have arrested hundreds of Islamic terrorism suspects, many in connection with the Madrid attack.

In recent years police have also focused on cells suspected of recruiting mujahedeen fighters and suicide bombers, or of collecting money to finance Al Qaeda-linked groups abroad.

The Madrid train attacks were claimed by Muslim militants who said they had acted on behalf of Al Qaeda to avenge the presence of Spanish troops in Iraq, but Spain's courts found no evidence Al Qaeda ordered or financed the attacks.