Is Afghan Gov't Coming to Aid of Bombers?

It's what American soldiers call a security bubble. To Afghan shopkeepers and their children it's a chance for a normal life. In a string of villages south of Kabul, U.S. troops are providing security in return for help in hunting the Taliban, reports CBS News national security correspondent David Martin.

It's a small scale model of what Gen. Stanley McChrystal is calling for in his strategic assessment -- a greater concentration of U.S. forces working closely with Afghan soldiers and police. According to Captain Paul Shephard, it began here with a massive increase of U.S. troops.

"We've seen a complete 180 and we've seen that because one, we flooded the area with soldiers. We've gone from 500 to 5,000," Shephard said.

But outside the bubble, this province is still a very dangerous place. U.S. troops have been here since the beginning of the year, watching down on the roads and clearing them of mines. But just three days ago, at almost this same spot, a roadside bomb killed Army Specialist Abraham Wheeler and seriously wounded CBS radio reporter Cami McCormick.

Listen: Cami McCormick reports on the increasing danger from roadside bombs

Listen: Cami McCormick reports on the growing number of U.S. casualties in Afghanistan

Lt. Col. Tom Gukeisen told CBS News three men were arrested after a search by the Afghan army brought in suspects with evidence on their hands.

"There were three individuals there that had explosives three times the normal limit or tolerance levels for TNT," Gukeisen said.

Martin watched as a team of investigators boarded a helicopter carrying the physical evidence, including fingerprints, that could convict the three men of murdering an American soldier and wounding a U.S. citizen -- except one of the bombers had a cell phone with a number to the Ministry of Defense in Kabul. That might explain why a letter arrived from the Ministry saying they'd arrested the wrong man.

"We think he was tied to the Ministry of Defense," Gukeisen said. "Someone in that office that began to put political pressure."

The three are still in U.S. custody and could be put on trial. But U.S. officers say there will be neither justice nor security -- no matter how many American troops -- if the central government pulls strings for roadside bombers.