
Berlin (CNN) -- Two men arrested in Berlin on suspicion of plotting a bomb attack must remain in custody, a judge ruled Friday.
Police now have up to six months to investigate the case, said Robert Baml, spokesman for Berlin's justice department. The chance that they would escape was a factor in the decision because "we can confirm the suspects went abroad with faked passports for several times," Baml said.
The suspects, a 24-year-old German of Lebanese descent and a 28-year-old man from Gaza, were arrested Thursday as police searched an Islamic cultural association and two other addresses in Berlin.
A German intelligence source told CNN that Berlin police found chemicals that could "definitely be used to make a bomb."
The intelligence source and a police source said faked Bulgarian passports were found and police are investigating computers and USB flash drives.
"The arrest of the two suspects after month-long shadowing is a huge success for Berlin's police," said Bernhard Witthaut, federal chairman of the German police union.
"Lots of work has been done over the past months. But it is important that all Germans stay attentive. It is better to call the police one time too often than to stay passive."
The pair, whose names have not been made public, had tried to obtain chemicals that can be used to make a bomb, Berlin Police press officer Martin Otter told CNN after their arrest.
Otter said Friday that liquid was found in the flat of one of the suspects but did not say what that liquid might be used for.
About 230 officers were involved in the police operation, codenamed "Shower of Rain," he said.
He declined to comment on a report by German newspaper Bild that suggested the most important tip came from a foreign intelligence service.
Speaking Thursday, Otter said the suspects are not thought to have any links to international terrorist organizations and police do not believe they had a specific target.
Police spokesman Thomas Neuendorf told CNN that law enforcement officers had been monitoring the men for months. The pair came under suspicion after they sought to acquire a large amount of cooling agent, he said.
The arrests were made in the Kreuzberg and Neukoelln districts of Berlin, Neuendorf told reporters outside the Islamic center.
The center was searched because police believed the suspects might have stored some chemical material there, as it had a lot of space, he added.
Neuendorf said many papers had been found but no explosives. The public prosecutor's office for Berlin is investigating the case, he added.
A German intelligence official, who did not want to be named because he was not specifically authorized to talk to the media, told CNN the suspected plot was thought to be Islamist.
Berlin's Al Rahman mosque was visited by investigators as well as the Islamic center, the intelligence official said.
There has been increased concern in recent years over homegrown, al Qaeda-inspired terrorism in Germany, he said.
German counterterrorism officials are especially concerned by the spreading influence of the English-language AQAP (al Qaeda in the Arabian Peninsula) Inspire online magazine in Germany, which gives instructions on how to carry out an attack, he added.
With the 10th anniversary of the September 11 attacks on the United States approaching, many security services around the world are on a heightened state of alert.
CNN's Rick Noack and Stephanie Halazs, and CNN security analyst Paul Cruickshank contributed to this report.
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