A Spanish judge indicted 32 people for allegedly plotting to drive a truck packed with explosives into a courthouse that has been the hub for anti-terrorism investigations, authorities said Tuesday.

The 32 men, mostly Algerians, were charged with membership in a terrorist organization, conspiracy to commit a terrorist attack and forgery of public documents, Judge Fernando Grande-Marlaska said in his March 13 ruling.

The suspects include Mohamed Achraf, the alleged mastermind who was extradited from Switzerland to Spain in April.

Spanish authorities suspect Achraf was planning to ram a truck loaded with 1,100 pounds of explosives into the court in downtown Madrid.

Grande-Marlaska has previously said such an attack could have killed 900 people.

Spanish judge Baltasar Garzon has said other possible targets for the group included Real Madrid's soccer stadium and a political party's headquarters.

Garzon claimed Achraf set up a terrorist cell known as the "Martyrs for Morocco" in 2003 while serving time in a Spanish prison for credit card fraud between 1999 and 2002.

Garzon said the cell had links with other Islamic terrorists, including the group believed to be behind the March 11, 2004, train bombings in Madrid that killed 191 people.