Police reportedly now suspect at least six Moroccans took part in the Madrid train bombings (search), and the United States is assisting a growing international investigation that is increasingly focused on Islamic militants possibly linked to Al Qaeda (search).
A 45-year-old woman died of her injuries Tuesday, raising the death toll from Thursday's bombings to 201. Of the more than 1,600 wounded, eight are in critical condition.
Cardinal Antonio Rouco Varela led a Mass at Madrid's cathedral Tuesday night remembering the victims of the bloodiest terrorist attack in Spain's history.
"The tragic attacks of March 11 have sunk us all into deep pain," intoned Varela, a huge black ribbon hanging from a wall above the altar. "To kill your own kind, to kill a brother, is to attack God himself."
The main suspect in custody in the attacks, Moroccan immigrant Jamal Zougam (search), has already been identified by Spanish Judge Baltasar Garzon as a follower of Imad Yarkas (search), the alleged leader of Spain's Al Qaeda cell who is jailed on suspicion he helped plan the Sept. 11, 2001, attacks on the United States.
The daily newspaper El Pais reported Tuesday that police believe they have identified five other Moroccans who directly participated in the attacks and are at large. Spain's Interior Ministry refused comment.
Two people who were traveling on one of the attacked trains have said that Zougam was aboard just before the bombs began exploding, El Pais said.
With signs that the bombings were carried out by Islamic extremists who operate and have confederates in several countries, FBI agents are helping Spanish police in using fingerprints and names to seek a full picture of Zougam and four other suspects in custody, a senior U.S. law enforcement official said in Washington.
Spanish police have also arrested two more Moroccans and two Indians, but their possible role in the attacks has not been specified. European countries were searching their databases for any information pertinent to the attack.
A U.S. official, speaking on condition of anonymity, said "it's increasingly likely Islamic extremists were involved in these attacks. In terms of assigning responsibility, it isn't clear."
"It's not clear who these groups were," the official said, referring to whether they had links to Al Qaeda and other extremist groups or even to the Basque separatist group ETA.
A suspected link between the Madrid bombings and homicide bomb attacks in Casablanca, Morocco, last year grew stronger Tuesday when French private investigator Jean-Charles Brisard described a phone tap in which Zougam said he had met with Mohamed Fizazi, the spiritual leader of Salafia Jihadia, a clandestine Moroccan extremist group.
Salafia Jihadia is suspected of involvement in the Casablanca attack, which killed 33 people and 12 bombers and has been linked to Usama bin Laden's Al Qaeda terror network.
Brisard told The Associated Press the tapped call is cited in a lengthy report written for Garzon's inquiry of the Sept. 11 attacks. Brisard, who is helping investigate the Sept. 11 attacks for lawyers representing some victims' families, has a copy of the report.
The Garzon document says that in the August 2001 monitored phone call, Zougam told Yarkas: "On Friday, I went to see Fizazi and I told him that if he needed money we could help him with our brothers," Brisard said.
Fizazi was among 87 people sentenced in Morocco in August in a trial that centered on the Casablanca attacks. Fizazi received a 30-year sentence after being convicted of preaching radical Islam in mosques and meeting with the Casablanca attack's perpetrators.
Police in the Basque city of San Sebastian, meanwhile, said they detained an Algerian who allegedly talked about a terrorist attack in Madrid two months before it happened.
Ali Amrous, an apparent indigent, was picked up Monday to learn if he had advance knowledge of the attacks, police said. He was first arrested in January after a neighborhood disturbance and while being questioned told police, "We will fill Madrid with the dead," according to authorities.
He was expected to be brought to Madrid for questioning. Police said they did not believe Amrous had any contacts with ETA, which the government initially blamed for the attacks.
Authorities have been tracking Islamic extremist activity in Spain since the mid-1990s and say it was an important staging ground, along with Germany, for the Sept. 11 attacks.
The Madrid attacks are now one death short of the 202 killed in October 2002 in the nightclub bombing in Bali -- blamed on an Al Qaeda-linked group -- which was the deadliest terror attack since Sept. 11, 2001.