The insurgents who attacked the U.S. Embassy in Kabul last week were killed but their cell phones left a trail.
The phones had been used to call Pakistani intelligence operatives before and during the assault. This evidence lies behind the charge made by Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, that the Haqqani network is a "veritable arm" of Pakistani intelligence, CBS News national security correspondent David Martin reports.
The attack on the U.S. Embassy and NATO's Afghan headquarters resulted in a 22-hour firefight - with American troops pinned down on roof tops.
Sixteen people were killed -- no Americans -- but the buildings in the embassy compound were damaged.
According to U.S. officials, the Haqqani network consists of several thousand fighters and operates with impunity from safe havens inside Pakistan, conducting cross-border raids into Afghanistan and up into Kabul.
The Pakistani spy agency uses the Haqqanis to sow violence so Afghanistan cannot emerge as a strong and stable country allied with Pakistan's arch enemy India.
Two days before the attack on the U.S. Embassy, a large truck bomb went off at an American combat outpost, wounding 77 U.S. soldiers.
Two days before that, U.S. intelligence intercepted communications that the Haqqani network was sending a large truck filled with explosives into Afghanistan. Gen. John Allen, the commander in Afghanistan, called Gen. Ashfaq Parvez Kayani, the commander of Pakistan's army and former head of Pakistani intelligence, and asked Kiyani to head off the attack. According to U.S. officials, Kayani promised to "make a call," but the truck continued into Afghanistan and exploded on the anniversary of 9/11.
These are only the latest in a long stream of high-profile attacks by the Haqqani network which U.S. officials say is protected and financed by Pakistani intelligence.
Just this past Friday at a meeting in Spain, Adm. Mullen met with Kiyani and complained about Pakistani support for the Haqqani network. Kayani replied that he understood but made no promises to do anything about it.
Now that Mullen has gone public with his complaints, Kayani has issued a statement saying they are not based on fact and accusing Mullen of playing a blame game.
In New York for the U.N. General Assembly meeting, Pakistani Foreign Minister Hina Rabbani Khar denied accusations her country attacked the embassy and deemed them "exceptionally hostile." Khar said the U.S. charges come from a desire to want to use Pakistan as a scapegoat for the fighting in Afghanistan.
"We are part of the solution," Khar told CBS Evening News anchor Scott Pelley. "We are not part of the problem. And if you continue to drive us in the other direction, unfortunately you will not only alienate the government of Pakistan, which is reaching out to you, which has been a worthy ally. I'm more concerned you will [alienate] the 180 million Pakistanis that your government always talks about reaching out to."
Watch more from Scott Pelley's interview with Hina Rabbani Khar: