Police questioned three people over the deadly bombing of Benazir Bhutto's caravan, which killed at least 136 people and shattered what was intended to be a triumphant return from exile.
The men were linked to a vehicle that police believe was used by one of the attackers who threw a grenade at the convoy late Thursday, causing Bhutto's campaign bus to come to a halt, said a senior investigator who spoke on condition of anonymity Saturday because of the sensitivity of the investigation. Seconds later, a suicide bomber blew himself up with a shrapnel-filled explosive.
Police detained the three men in southern Punjab province - a center for militancy - and took them to Karachi for questioning.
The senior investigator said police believed the men, who have yet to be charged, hold crucial clues to the bombing.