Madrid, Spain (CNN) -- A judge at the Spanish National Court took statements Friday from three men who may have been plotting terrorist attacks on British and U.S. targets, an Interior Ministry spokeswoman said.
Judge Pablo Ruz has not yet decided whether to prosecute the defendants, a court spokesman said.
Two of the men were arrested Wednesday and the third Thursday. The case has been called one of Spain's largest operations against al Qaeda, according to Spanish Interior Minister Jorge Fernandez Diaz.
The investigation is now focusing on finding the explosives that the three suspects may have hidden, police sources said. Spanish police were searching a construction company in Gibraltar.
The Interior Ministry said the men were "ready to act in Spain and Europe." One of the men is Turkish, and the other two are believed to be of Russian-Chechen origin. Police sources said they had gathered enough explosives to "blow up a bus."
Authorities later identified the Turkish national as Cengiz Yalcin, and the others are Ahmad Avar and Muhammad Adamov.
Avar, who was apparently once apart of Russia's Army Special Forces, an expert in poison and a trained sniper, is thought to be the head suspected al Qaeda cell. He had been living in Spain for two months, police said.
Adamov, authorities say, had received "intensive training in the camps of Afghanistan where he became an expert in managing explosives." He is also suspected to have had a hand in the recent Moscow bombings.
The two Chechen men arrested Wednesday were on a bus traveling to France when police detained them.
Authorities say they "resisted fiercely."
Police sources added that they were stopped in Almuradiel, a town about midway between Madrid and the country's southern coast.
The third was held in the province of Cadiz on Spain's southern coast.
Yalcin said Friday that he had no knowledge of explosive substances found during a search of his home, according to source briefed on the court proceedings.
He added that he enjoys ultralight aircraft and remote-controlled airplanes, had equipment in his home used for three motor-powered paragliders and had wanted to teach his Chechen friends how to fly them.
Authorities say they believe Yalcin had been the logistics man of the group, and had been living legally in Spain where he worked for a construction company in Gibraltar.
The two Chechen men claimed that they were in Spain to apply for political asylum, and one acknowledged that he had been in Afghanistan, the source said.
All three have denied al Qaeda links.
Prosecutors have asked to be allowed to hold the Chechens for two more days to allow police to root out more evidence in their investigation, partly because certain intelligence exchanges are not considered admissible in court.
Police are currently trying to unlock the contents of 32 GB thumb drive that belongs to one of the Chechen suspects, according to Fernando Reinares, a senior international terrorism analyst at The Elcano Royal Institute in Madrid, who was briefed by Spanish security services on the investigation.
There are indications from intelligence developed in the investigation that one of the Chechen men attended a Lashkar e Taiba training camp, Reinares said.
The group is a Pakistan-based militant organization accused of multiple high-profile attacks, particularly those against neighboring India.
Authorities think France may have been the first target of the cell because suspects were traveling there. Spanish and French intelligence officials are still analyzing a laptop and documents located in the apartment of the Turkish suspect in San Roque, Cadiz.
The investigation is in its early stages, but Spanish security services have said that the men were most likely plotting to attack the joint U.S.-Spanish naval base at Rota or British interests in Gibraltar, according to Reinares.
CNN Terrorism Analyst Paul Cruickshank and Journalist Javier Ruiz contributed to this report