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• Slogging through rugged terrain
• No evidence Rudolph being helped
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ANDREWS, North Carolina (CNN) -- Sophisticated helicopters, similar to those used to penetrate the thick foliage of Vietnam, may be recruited to help in the manhunt for bombing suspect Eric Robert Rudolph, CNN has learned.

More than 200 federal and local law enforcement officials have been searching without success for Rudolph in a mountainous, heavily forested area of southwestern North Carolina, where he was last spotted July 7.

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Helicopters with infra-red equipment, which can detect human body heat, have been used during nighttime searches, in an attempt to detect Rudolph among the trees. But heavy rock formations in the area retain daytime heat, triggering false readings.

Authorities are now considering bringing in the new helicopters equipped with more sophisticated equipment, a source tells CNN.

Rudolph, 31, of Marble, North Carolina, is wanted in connection with an explosion January 29 at a women's clinic in Birmingham, Alabama, where abortions are performed. A security guard was killed and a nurse severely injured.

He is also wanted for questioning in three other bomb attacks in Atlanta in 1996 and 1997 -- at Centennial Olympic park, a women's clinic and a bar with a mostly lesbian clientele.

Federal agents say those attacks appear to share similarities with the Birmingham blast. A woman was killed and more than 100 other people were injured in the blast during the summer Olympic Games.

Rudolph

On July 7, Rudolph came out of hiding and contacted George Nordmann, a former neighbor who lives on a lake near Andrews, asking for food. Four days later, after his pickup truck was taken -- possibly by Rudolph -- Nordmann contacted local authorities, triggering the latest massive search.

Authorities haven't officially responded to questions about a significant lag between the first time Rudolph approached Nordmann and the time when the 71-year-old Nordmann notified police.

Woody Enderson, chief of the task force investigating the bombings, said Saturday that the rugged terrain around Andrews was making the manhunt slow and arduous.

He characterized the area as "very rugged terrain and heavily wooded forest, steep mountains, a number of areas difficult to traverse and miles of mountain trails and roads."

"Within the search perimeter are some of the obstacles that must be surmounted daily as our work advances," he said. "On several occasions in the past few days, search teams have had encounters with rattlesnakes, but, fortunately, none of the searchers have been injured."

On Saturday, search teams could be seen going into the woods at several locations, equipped with backpacks.

Federal agents search Nordmann's property

On Friday, a bloodhound was taken to the woods near Nordmann's home. The dog appeared to pick up a scent but eventually lost it at a nearby creek.

Rudolph grew up in this remote corner of North Carolina, where conservative Christianity and anti-abortion sentiments run deep.

While law enforcement officials have not said they have evidence that anyone is helping Rudolph hide, some locals have openly admitted they would feed and protect him if he came to them for help.

"I've had people tell me, 'Homer, I've known you all my life and I respect you. But if I knew where he was, I wouldn't tell you,'" said Sheriff Homer Holbrooks of nearby Macon County.

Correspondents Art Harris and Aram Roston contributed to this report.