WALLDORF, Germany -- A Turkish man and his American fiancee arrested for plotting to bomb U.S. military bases in Germany on the anniversary of the Sept. 11 attacks appear to have no link to the al-Qaida terror organization, authorities said Saturday.

The pair were arrested on Thursday by German police who were tipped off by U.S. authorities. Hundreds of pounds of bomb-making chemicals, five pipe bombs and a picture of Osama bin Laden were found in the couple's apartment near Heidelberg, officials said.

But German Interior Minister Otto Schily said there was still no evidence they had been recruited by the network.

"Based on what we know so far, we are dealing with an individual who has shown no indication of participation in a terrorist network," Schily told Antenne Bayern radio. "It seems that we are dealing with a dangerous individual with an Islamic background."

However, federal investigators said they were reviewing the evidence and could take over from local authorities if a link to a terror network were discovered.

"It must be clarified whether the male suspect acted alone, whether the two acted together or whether they planned the terror attack in Heidelberg as members of a terror organization," federal prosecutors said in a statement.

German television ZDF reported that investigators were looking into possible links between the male suspect and an Islamic center in Heidelberg that was previously under investigation for allegedly helping finance the 1998 bombings of two U.S. Embassies in Africa.

Tipped by U.S. authorities, German police arrested Oman Petmezci, 24, and his American fiancee, identified as Astrid Eyzaguirre, 23, on Thursday in the apartment they shared in Walldorf, about six miles south of Heidelberg, home to the U.S. Army Europe headquarters in southwestern Germany.

According to German television ARD, U.S. security officials were questioning Eyzaguirre. A spokesman for the U.S. Army declined to comment on the report.

Inside the couple's third-floor apartment, where visitors are greeted by a Sylvester and Tweety cartoon welcome mat outside the door, police found 287 pounds of chemicals and five pipe bombs, a book about bomb-making and a picture of Osama bin Laden.

It was unclear how much damage the chemicals could have done as explosives since the names of the chemicals were not released.

The German weekly Der Spiegel reported Saturday that a friend of Eyzaguirre's told U.S. military police the arrested woman had warned her to stay away from the military shopping area for the next few days.

Eyzaguirre worked at a base store and had access to many facilities at Campbell Barracks, which besides the Army headquarters also contains the Army's 5th Corps headquarters and a NATO facility. Petmezci worked at a chemical warehouse in Karlsruhe, state investigators said.

Neighbors in Walldorf, a town of 14,000 that houses a large American military community, described the pair as "pretty friendly." But one man recalled that Petmezci openly discussed his hatred of Jews.

Despite Petmezci's Islamic beliefs, Juergen Meyer said they'd drunk beer together watching soccer -- and that in the context he didn't take the talk seriously. "I thought it was all nonsense."

Jessica Rosarius, who lives on the same floor as the couple, said she saw Eyzaguirre standing in the hall outside her third-floor apartment shortly after noon on the day of the arrests.

"I asked her if she locked herself out and she said, 'Long story,"' said Rosarius.

As she left the building, Rosarius said she saw several police vans and a police dog unit, but did not see authorities remove anything from the apartment.

Though both Rosarius and Eyzaguirre are German-Americans, roughly the same age, living in the same building and working on base in civilian jobs, Rosarius said their interaction was confined to casual greetings and that neither had visited the other's apartment.

Nor, Rosarius said, did she ever pick up any anti-American sentiment from Petmezci. "They were normal, just friendly together," she said.

Campbell Barracks, at the heart of the military community of 16,000 nestled in the green hills of southwestern Germany, remained on a low-level alert.

"I expect people are a little more alert, but there has not been a visible increase in security," said U.S. Army Europe chief spokesman Sandy Goss.

Some were worried, however.

"When Sept. 11 happened, we were shocked beyond words, but we were a long way away and now we're not," said Wanda McCollar, a teacher at the high school for kids of servicemen and women. "The reality is closer to where we eat and sleep."

U.S. counterterrorism officials in Washington said Friday they detected a mild increase in the terrorist "chatter" in the run-up to Sept. 11, but don't believe it is a sign of a major impending attack.

The "chatter" -- intelligence from various sources that monitor suspected terrorists' communications -- fluctuates often and was far greater around the July 4 holiday, one official said.

While officials are concerned al-Qaida may try an attack on the anniversary of Sept. 11, they note the group has never marked anniversaries or holidays, unlike other terrorist organizations.

Federal law enforcement officials have issued no major terror alerts to local police in recent days, according to a Justice Department official.