Pakistani authorities now suspect that two suicide bombers were involved in a bloody attack on former premier Benazir Bhutto’s homecoming convoy, officials said on Monday. Officials had earlier said only one of the two blasts that killed 139 people in Karachi on Thursday was carried out by a suicide attacker, while the other was caused by a grenade hurled by an unknown assailant. “We have got another head which we suspect could be of a second suicide bomber,” Sindh Home Adviser Wasim Akhtar told AFP. “We have suspicions about it and our investigators are making fresh efforts. His face is being reconstructed but so far we have got no substantial clues about those behind the blast,” he said. Police at the weekend released a photograph of the other bomber’s blood-streaked head. Police officials speaking on condition of anonymity also said the second head found at the scene was believed to be that of another suicide bomber. Bhutto had previously claimed that two suicide bombers were involved and has called for international help in the inquiry into the bombing.