You can survive without air for four minutes. You can survive four days without water. And you can survive four weeks, we are told, without food. But there are hundreds of people tonight in oklahoma... See More
You can survive without air for four minutes. You can survive four days without water. And you can survive four weeks, we are told, without food. But there are hundreds of people tonight in oklahoma still holding out hope they will hear a human voice, and they are not going to go by any numbers. Abc's mike boettcher spent all day with them. Mike? Reporter: Well, diane, they did indeed search all day long, and they made a vow. That they will search every destroyed and damaged home in moore, until they're able to determine that no one is left behind. And this, what they're trying to do, is to find a miracle in this city. They searched all night. Hoping for something. A murmur. A quiet call for help. And they searched all day. But as time passed, expectations changed. Hey! Reporter: Tiptoeing across a high wire of debris, they looked and listened hard for signs of life, but there were none. We're trying to find any shelters that are possibly still covered up. Or anyone that is just trapped in place. Through his partner, equally agile, traversing splintered houses, finding nothing was what he hoped for. What could be the best thing that could happen to you out here on this search? Not finding anything. That would be the best thing. Reporter: Captain harvey had to agree. Best case scenario, you just find a bunch of debris. Reporter: It's a hard truth of search and rescue. The chances of finding life diminish with each passing minute, but still in quiet, they press on. It is their calling. It's late may, wet, cold, and we're walking through a disaster area. Why do they do it? I'm a hometown oky, and we're all part of a larger family here. Reporter: As the weeks pass, thoughts of this disaster will slip from the public's mind. It always does. But these men and women aren't the general public. And they will always live with what they saw here. They will continue their search all night long.
This transcript has been automatically generated and may not be 100% accurate.