MESA VERDE NATIONAL PARK, Colo. - High humidity and a little rain Tuesday helped firefighters partially contain a 5,000-acre wildfire burning on the nation's largest archaeological preserve and threatening several ancient cliff dwellings.
The fire burning in Mesa Verde National Park and Indian reservation land was 40 percent contained by evening, park spokesman Will Morris said.
Full containment was predicted for 6 p.m. Friday.
''It's looking good, but nobody's letting down their guard,'' Morris said.
Incident commander Mike Lohrey warned the ancestral Pueblo Indian cliff dwellings and park buildings could still be threatened if hot spots scattered throughout the canyons flare up.
Firefighters were ferried by helicopter to a site where they continued digging a line around the flames to contain the blaze.
The humidity was expected to remain high Wednesday and Thursday, with rain forecast for Thursday, boosting hope the fire would be contained by the end of the week.
''I think we're turning the corner,'' Lohrey said.
None of the park's major cliff dwellings near Wetherill Mesa has been damaged in the fire, although in some cases the flames burned on the mesas above the dwellings and in the canyons below but did not get inside.
About 460 firefighters are battling the blaze.
Park archaeologist Linda Towle said the cliff dwellings surviving the fire comes as no surprise.
''That's probably the reason why these sites were built in the alcoves,'' Towle said. ''It provides protection from heat in the summer, cold in the winter, and now, we know, protection from fire.''
The sandstone homes are built back in alcoves in the cliffs, which provides a natural shield, Towle said. The most flammable parts of the dwellings are the wood beams and poles inside.
Fire burned a four-to five-room dwelling built next to a rock outcropping in a canyon that is not open to the public. Archaeologists could not reach the dwelling, called ''Mushroom Site,'' to assess the damage because the fire was still burning inside.
Towle said archaeologists had just completed a study of the site and the park has a good record of what it looked like.
Members of the Ute Mountain Ute Indian tribe, who live on a reservation southwest of the park, have not had enough money to go into their tribal park to assess the cliff dwellings there, said Doug Bowman, the tribe's senior archaeologist.
The reservation, where the lightning-sparked fire began on Wednesday, has sites similar to the national park that have never been surveyed or studied extensively, Bowman said.
''There was no fence line,'' Bowman said, adding that the 125,000-acre park is rich in archaeological sites.
The fire has scorched about 4,000 acres on tribal land and about 1,000 acres on the park, Lohrey said.
The fire did destroy the 70-year-old winter house of former tribal chief Jack House on the reservation and a pavilion on Wetherill Mesa in the park where tourist wait for a shuttle to Long House. The pavilion contained a ranger station, a snack bar, a small bookstore and picnic tables.
The park remains closed indefinitely.
The fire is the second to strike the park in a month. The earlier blaze burned 23,000 acres of public and private land on the northeast side of the park but spared its archaeological treasures.
Based on a 1996 fire, when archaeologists found 400 new sites, Towle estimated the two fires this summer could ultimately lead to the discovery of 2,000 sites.
Archaeologists continued to travel with fire crews Tuesday, marking the location of artifacts found. The fire line was being built around those sites.