GUATEMALA CITY - Illegal settlers likely working for drug smugglers are starting fires to clear land in the Guatemalan jungle and threatening investigations into an ancient Mayan city with soaring pyramids and temples.

U.S. and Guatemalan archaeologists who trekked to the La Corona site in northern Guatemala to map dozens of huge Mayan ruins had to trade their scientific instruments for machetes and buckets of water last week to fight an encroaching blaze.

They fought the fire for two weeks, helped by natural dirt barriers and rains that calmed the flames, but land invaders deep in the lawless jungle simply lit more fires, dangerously close to the more than 1,200-year-old Mayan site.

"We were able to bring some of the fires under control but the invaders just lit them up again. The rains have helped but there is still a threat," said Mariela Lopez, a director of the forest protection service for the northern Peten department.

The Peten region, which teems with wildlife like jaguars and scarlet macaws, has become a favorite trafficking route for drug cartels.

Smugglers clear jungle to build clandestine airstrips to land small planes loaded with cocaine which is then trucked over the porous border with Mexico and up to U.S. consumers.

Drug gangs, and people supporting them who live illegally in the 800,000-acre Laguna del Tigre park, which surrounds the La Corona site, see the archaeologists as a threat.

"At our archaeological base camp we have guards and that creates a problem for these people. That kind of permanent presence could detect what they are doing," Tomas Barrientos, the Guatemalan head of the La Corona project, told Reuters by telephone.

Slash-and-burn tactics mean vegetation in northern Guatemala is disappearing at one of the fastest rates in the world.

Smuggling has been rife in the area since the 1960s when looters raided the buried temples at La Corona and sold the stolen merchandise to private collections.

Archaeologists searched for the site for decades after discovering a series of looted Mayan sculptures from 600 to 900 A.D. in U.S. and European museums, all carved from stone and showing similar features.

In 2005, investigators identified La Corona as the site they were hunting for, after finding a panel there with the same strange snakehead glyph as the stolen sculptures.