Security may be tighter at the base Friday, but U.S. officials still don't know exactly how a suicide bomber managed to get in without being searched, killing.
One former intelligence official tells CBS News initial reports indicate the bomber was being recruited as a CIA source.
And a Pakistani Taliban commander Friday praised what he called their He said the bomber was avenging the killing of Taliban leader Baitullah Mehsud in a U.S. drone strike last August.
Taliban sources tell CBS News the notorious Haqqani network was behind the attack, using Afghan operatives with the help from colleagues in Pakistan.
The Haqqani group covers both sides of the Afghan-Pakistan border, reports CBS News correspondent Kimberly Dozier. U.S. officials say the group is responsible for everything from suicide and roadside bombings to the capture of U.S. Private Bowe Berghdal.
U.S. commanders say they've been stepping up attacks against the Haqqanis, sending an extra 1,000 special ops forces across Afghanistan over the past year. Another 500 are due this spring. A senior U.S. official says the Paksitani government has also agreed to allow small numbers of U.S. special ops forces to operate on the ground in the Haqqani's Pakistan stronghold.
Forward operating base Champman was key to gathering intelligence against the Haqqanis and coordinating drone strikes. That mission has been made much more difficult.
"The bottom line is this was a really important target," said Christine Fair of Georgetown University. "They knew what they were doing when they went after this particular base."
While intelligence collection may be disrupted it has not stopped operations. A Taliban commander told CBS News a U.S. drone strike Friday in Pakistani territory took out another top Taliban commander from the Haqqani network.
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