Can't find confirmation, but I heard this attack described as the single biggest loss to the the CIA since the Vietnam war:

(CNN) -- An attack by a suicide bomber at a military base in eastern Afghanistan on Wednesday killed eight Americans believed to be CIA employees, a senior U.S. official told CNN.

Also Wednesday, four Canadian soldiers and a Canadian journalist were killed when a roadside bomb hit their armored vehicle in southern Afghanistan, Canada's defense ministry said.

The suicide bombing happened at Forward Operating Base Chapman in Khost province, Afghanistan. The senior U.S. official who spoke to CNN said information indicates the bomber walked into a gym facility at the base and detonated a suicide vest. It is believed six Americans were wounded in addition to the eight killed. It's not known how the bomber got past security.

A U.S. military source said that FOB Chapman was originally a base for the Khost Provincial Construction Team, but the team left some time ago.

Authorities believe that perhaps the suicide bomber attacked just after a convoy was ending or beginning, which would account for high number of casualties.