Madrid -- Spanish police have arrested four more suspects, believed to be of Moroccan origin, in the Madrid terror bombings[. . . .]

The four arrests take the total number of people in custody to 10. They include three Moroccans and two Indians arrested Saturday [and since, released], two days after the bombing, and an Algerian being quizzed to see whether he had advance word of the attack.

[. . . .] The key suspect is Moroccan Jamal Zougam, 30. Spanish police were reported to have been seeking another 20 people -- nearly all Moroccan -- for questioning.

Spanish law enforcement agencies were aware of Zougam's alleged links to Osama bin Laden's al-Qaeda terror network since at least 2001, when they searched his Madrid apartment. They found videos, including one that contained a bin Laden interview, and phone numbers for suspected al-Qaeda members.

Later Thursday, Judge Baltasar Garzon was to quiz Imad Yarkas, the alleged leader of al-Qaeda's cell in Spain. Mr. Yarkas is in jail on suspicion that he helped plan the Sept. 11, 2001, attacks in the United States.

Mr. Zougam and Mr. Yarkas have known each other since at least 2001, according to Judge Garzon's painstaking probe of al-Qaeda operations in Spain. [. . . .]

Mr. Zougam also is suspected of having links to Said Chedadi, another alleged al-Qaeda operative arrested with Mr. Yarkas on Mr. Garzon's orders in 2001. [. . . .]

Moroccan authorities say they suspect Ansar al-Islam, an Islamic extremist guerrilla group blamed for terrorist strikes in Iraq, Jordan, Turkey and Morocco, of being behind the Madrid bombings.

Moroccan officials said evidence shows Mr. Zougam had links to Abu Musab al-Zarqawi ? a key operative with strong ties to Ansar.

The officials, who spoke on condition of anonymity, believe the perpetrators of the March 11 attack in Madrid also have ties to those responsible for suicide bombings in Casablanca, Morocco, that killed 33 people and 12 bombers last May.