updated 3:54 p.m. ET July 1, 2008

LIMA, Peru - An influx of tourists to Peru's famed Inca citadel of Machu Picchu may prompt UNESCO to add the jungle-shrouded ruins to its list of endangered World Heritage sites.

Yearly visits to Machu Picchu, Peru's top tourist destination, have more than doubled since 1998 to 800,000 people, and conservationists advising UNESCO's World Heritage Committee warn that landslides, fires and creeping development threaten the site.

UNESCO officials will discuss those findings this week at a World Heritage Committee meeting in Quebec City that was called to determine which of the world's cultural treasures should be added to its list — and which of those already included there are now threatened.

UNESCO committee spokesman Roni Amelan declined to confirm that Machu Picchu, which was named a World Heritage Site in 1983, would be classified as endangered, but said "it's a possibility."

Unregulated growth, including a boom in hotel and restaurant construction in the nearby mountain town of Aguas Calientes, is putting pressure on erosion-prone riverbanks and could undermine the site, the report said.

The village lacks adequate sanitation and Peru's government has done little to address landslide concerns on the winding, mud thoroughfare that leads to the citadel, according to the report. Officials also have no way to detect fires in the stone citadel or its heavily wooded environs, the report said.

Residents in the nearby city of Cuzco, an ancient Inca capital, burned tires and blocked roads to protest state plans to extend private development near the site earlier this year.

But park officials note that while there may be room for improvement in Aguas Calientes, Machu Picchu itself is intact. Archaeologist Piedad Champi, who oversees conservation efforts, noted that UNESCO praised the monuments' preservation just last year.

Still, uncontrolled tourism could still degrade the ruins, said Luis Lumbreras, an independent, Lima-based archaeologist who has studied Machu Picchu for more than 40 years.

"Machu Picchu was never made for lots of people," he said, noting the original citadel was designed for sandals and bare feet. "If we put tourists with boots that are jumping, running, climbing the walls, et cetera, that's the danger."

A spokeswoman for the state-run National Culture Institute, which manages the park, declined to respond to UNESCO's advisory report. Peru's government has promoted the site as one of Latin America's top tourist destinations.

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