Karachi, Oct 21: Three people were detained for questioning in connection with the suicide attacks on the homecoming procession of former Pakistan prime minister Benazir Bhutto, in which 139 were killed and more than 500 injured.
According to media reports the men were linked a car from which a grenade was thrown in the city, seconds before the attacks were carried out.
Meanwhile, investigations were on in a list of three suspects named by Ms Bhutto.
Medical experts at Jinnah Postgraduate Medical Centre yesterday undertook the facial reconstruction of the bomber whose severed head was found from the site of the twin blasts.
Investigators also sent the finger-prints obtained from the forearms, believed to have been blown off from the body of the suicide bomber, to the National Database and Registration Authority, the Dawn newspaper reported.
Police Investigation chief Manzoor Mughal said that the first blast was caused by a Russian-made hand-grenade weighing around one kg.
The grenade explosion was aimed at breaching the security cordon around the specially-built bullet-proof vehicle of the Pakistan People's Party chairperson and other party leaders. The second blast took place seconds later, he added.
However, a senior police official speculated whether the first blast had been caused by a hand-grenade, arguing that the extent of damage was extraordinary.
Another police official Raja Umar Khattab said that he had recommended DNA tests on body parts obtained from the site of the blasts.
A high-ranking police official, part of Ms Benazir's security detail, said the bullet-proof vehicle of the PPP leader was stationary when the suicide bomber struck.
Two security vehicles fitted with jammers moved ahead of and behind Ms Bhutto's truck, which was flanked by four to five police vans at a time, he added.
The first blast took place on the right side of the truck.
The second explosion, which led to greater devastation, took place on the left side of the truck. Ms Bhutto was immediately whisked away in a bullet-proof jeep, he added.
The police official said one vehicle fitted with the jammer was extensively damaged in the second explosion.
He conceded that the two jammers had broken down primarily because charged PPP activists had knocked over their antenna, installed atop the cars in which they were fitted.
But, he said, jammers could not have prevented Thursday's explosions because they had not been detonated by remote-controlled device. The explosives were manually detonated by the suicide attacker.
Five policemen sitting in the van close to the truck died on the spot while 27 other policemen were injured. They were part of Ms Bhutto's security cordon.
PPP activists gave the impression that the first blast was a tyre burst or an explosion in a pole-mounted transformer. The second explosion came as a rude shock, the police official added.
Another high-ranking investigator said that RDX, which is widely used in military and industrial applications, was employed in the suicide attack on the PPP leader.
The explosives, which weighed around 12kg contained ball-bearings and pellets, killed a large number of people and also left nearby vehicles pock-marked, he added.