Abu Musab al-Zarqawi, a Jordanian linked to Al Qaeda (search) and suspected of heading a terrorist network in Iraq, is now believed to have been the brains behind the deadly Madrid railway attacks, a French private investigator told The Associated Press on Friday.

Investigator Jean-Charles Brisard said Spanish officials told him some suspects held in the March 11 attacks were in contact with al-Zarqawi as recently as a month or two before the bombings, which killed 190 people and wounded more than 1,800.

"They believe today he was the mastermind," Brisard, who is probing the Sept. 11, 2001, attacks on the United States, said in a telephone interview from Geneva, Switzerland.

The Spanish Interior Ministry declined to comment on his assertions. "The investigation is at a critical stage," a ministry official said, speaking on condition of anonymity.

Late Friday, a Spanish radio station reported that police believe they have located the house where the bombs were built. Investigators found detonators and traces of dynamite inside the house near Alcala de Henares, 20 miles northeast of Madrid, radio network Cadena SER reported.

It said the attackers were believed to have used the building to prepare the explosives and stuff them into knapsacks. The investigators found the house a week ago, according to the report.

Brisard's comments came as the probe spread to Germany, a key staging ground for the Sept. 11 attacks on New York and Washington.

German police raided an apartment in Darmstadt where a Moroccan suspect arrested Wednesday in the Madrid train bombings stayed briefly last year. The 28-year-old man is suspected of membership in a foreign terrorist organization, a prosecutor said.

But German officials said they had no evidence that the Madrid attacks were planned or prepared in Germany.

Morocco, the native country of at least nine of the suspects, reported its first arrests in the case, although a senior official said they had not yielded significant information.

In Spain, authorities announced another arrest Friday, and a judge charged a 12th suspect in the case.

Spanish investigators believe six or seven of the 18 people now in custody in Spain helped plan the Madrid attacks and that al-Zarqawi was behind the plot, Brisard said.

In just two weeks, Spanish police say they have put together most of the pieces of the puzzle behind the bombings, according to Brisard, who is not a part of the investigation. "The picture is almost complete now," Brisard said.

"They are basically telling me that several of these people are talking a lot," Brisard said, referring to suspects he did not name.

Brisard is working for lawyers for relatives of Sept. 11 victims and has a copy of a dossier prepared by Spanish Judge Baltasar Garzon, who is investigating an alleged Al Qaeda cell in Spain. Garzon says the cell's alleged leader and other members helped prepare the Sept. 11 attacks.

Suspicion in the Madrid bombing has fallen on an Islamic extremist group from Morocco. The lead suspect, a Moroccan named Jamal Zougam, was described last year by Garzon as a follower of Imad Yarkas, the alleged leader of the Spanish Al Qaeda cell. The description appeared in an indictment returned in September against Yarkas, Al Qaeda leader Usama bin Laden and 33 other terror suspects.

The French investigator said the Garzon dossier showed that from 1996 to 2001, the Spanish Al Qaeda cell's alleged financier, Muhammed Galeb Kalaje Zouaydi, wired $100,000 to an operative in Denmark named Abu Khalet, who produced some 30 fake passports for al-Zarqawi and people close to him.

The passports were completed in late 2002 but it is not clear if al-Zarqawi received them, Brisard said.

U.S. officials blame al-Zarqawi for the March 2 bombings in Iraq that killed at least 181 Shiite Muslims. Ansar al-Islam, the group to which al-Zarqawi is linked, has often attacked Iraqi targets — Shiite pilgrims or Iraqi police — with the aim of sowing discord and perhaps civil war. Al-Zarqawi is also believed to have been behind the 2002 killing of Laurence Foley, a U.S. diplomat in Jordan.

At Spain's National Court on Friday, Judge Juan del Olmo charged suspect Faisal Alluc, a Moroccan, with collaborating with a terrorist group. He said he found insufficient evidence against another Moroccan, Khalid Oulad Akcha, who was returned to jail to continue serving time for unrelated, non-terrorism charges.

Hours later, a new arrest was announced but no details were disclosed about the suspect.

In Germany, authorities did not identify the suspect whose presence in that country triggered the raid Thursday night on an apartment in Darmstadt, south of Frankfurt. They said he had been registered since October as a resident of the apartment but apparently spent "only a few days" in Germany last fall.

Investigators are examining documents seized in the raid, said Horst Salzmann, a spokesman for federal prosecutors in Karlsruhe. He refused to say what role the Moroccan is believed to have played in the Madrid bombings.

Germany and Spain were believed to be important launching pads for the Sept. 11 attacks.

Investigators say lead hijacker Mohamed Atta (search) and other Sept. 11 plotters worked out of Hamburg, Germany before the attacks. Atta is known to have visited Spain twice in 2001, including a July visit that Garzon says was used to plot last-minute details in the devastating strikes on the World Trade Center and the Pentagon.