AP Source: 'Significant Blast' Killed CIA Agents

A federal law enforcement official says the explosion that killed seven Americans and a Jordanian at a secret CIA base in eastern Afghanistan was a "significant blast" set off as agents gathered outside a gymnasium.

The official said a small team of FBI agents that included bomb and evidence technicians flew to the site soon after the blast last week and have since returned. The official spoke on condition of anonymity due to the sensitivity of the investigation.

The official said FBI and CIA investigators are still trying to determine the components of the explosives and whether the bomber wore a suicide vest or belt. The official said the bomber apparently entered the base by car.