Nightly News | August 28, 2013
>>> tonight fire crews battling
>> tonight fire crews battling one of the largest fires in the history of california say it will likely be weeks before the fire is contained and new concerns about the smoke from this massive fire. nbc's miguel almaguer has more tonight from california.
>> reporter: the firefight on the front lines of the rim fire may not be over until winter. while there's steady progress in the push for containment.
>> look at those flames just ripping across those trees.
>> reporter: tonight growing concern far away from the fast-moving flames. at the hetch hetchy reservoir , the city of san francisco pristine water supply , there's no letup in the ash raining down. scientists are checking water quality for the 2.6 million who get their drinking water from here, but it's rain that gives them cause for concern.
>> the greatest risk of this fire is an enhanced input of sediment, which is essentially dirt from the forest floor in to the reservoirs.
>> reporter: where there's ash there's also smoke. this column shooting 30,000 feet into the air.
>> for hundreds of miles in both directions we just have smoke, ash and flames.
>> reporter: downwind in reno, nevada, 100 miles from the flames, bad air is forcing schools to cancel all outdoor activities. back near the blaze --
>> it's making my throat very, very dry and scratchy.
>> reporter: dozens have been hospitalized, all others warned to stay indoors.
>> there's definitely a higher risk of developing respiratory infections with all of the particular lit mat particulate matter in the air.
>> reporter: the smoke in this region could linger for months. with more than 280 square miles charred so far, firefighters are using new technology to survey the damage. drones like this one identify hot spots as fire reshapes the landscape, giving this region a new look, and new worries. tonight this fire has destroyed some 31 homes. it threatens 4,500 structures, it is just over 20% contained. lester?
>> all right, miguel, thanks for the update from there.
>>> up next, as we don't tonight from the nation's capital,