The detective leading the investigation into the bombings that targeted Benazir Bhutto as she returned to Pakistan has withdrawn from the case because of her objections, a senior official said today.
Ms Bhutto, a former Pakistani prime minister, escaped unhurt after the attack on her heavily guarded convoy in Karachi last Thursday. The explosions killed 138 people and injured around 300.
Javed Iqbal Cheema, an interior ministry spokesman, said Manzur Mughal had left the inquiry after Ms Bhutto complained that he had been present when her husband, Asif Zardari, was tortured while in custody in 1999.
"The investigation team will be formed anew after Manzur Mughal disassociated himself from the investigation in view of the objections raised by Benazir Bhutto on the chief investigator's credentials," Ghulam Muhammad Mohtarem, the home secretary of Sindh province, said.
Members of Ms Bhutto's Pakistan People's party (PPP) had also criticised Mr Mughal's handling of the crime scene.
Ms Bhutto accused factions within the military and the intelligence services of being involved in the assassination plot, and called for British and US experts to be called in to help with the inquiry. The Pakistani government refused her request.
At least 15 people are being held in connection with the attack, a police official said today.
The official, who did not want to be identified, said those held were being questioned, but none was currently being treated as a suspect.
Yesterday, authorities said the attack had probably been carried out by two suicide bombers. They released a picture showing the head of one of the suspected attackers, who had yet to be identified.
Security in Karachi remained high as Ms Bhutto revealed she had received another death threat. She said her lawyer had received a letter from an unidentified "friend of al-Qaida" threatening to slaughter her "like a goat".
The former prime minister said the writer claimed to be the "head of the suicide bombers and a friend of al-Qaida and Osama bin Laden".
She added that she believed her opponents were "petrified that the Pakistan People's party will return [to power] and that democracy will return".
Ms Bhutto's two governments, between 1988 and 1996, were toppled amid allegations of corruption and mismanagement.
She has returned to contest parliamentary elections due to take place in January, after months of power-sharing talks with the president, General Pervez Musharraf, that could see them forming an alliance in the next government.
However, any potential cooperation appears to have been strained by a war of words over who was responsible for Thursday's attack.
Ms Bhutto claimed figures from the government of Shaukat Aziz, the prime minister - backed by Gen Musharraf - could be implicated.
The chief of the ruling Pakistan Muslim League party, Chaudhry Shujaat Hussain, responded by accusing Ms Bhutto's husband of arranging the blasts to stir up public sympathy.
Concerns over rising religious extremism in Pakistan have paved the way for a deal between Ms Bhutto and Gen Musharraf.
In an indication of the challenges facing the president, Pakistan today said it had sent 2,500 troops into a remote valley in the north-west of the country to combat followers of a militant cleric, Maulana Fazlullah, who has called for Taliban-style rule.
Meanwhile, a provincial high court acquitted a man who was convicted of involvement in a deadly bomb attack on a Karachi Shia mosque which killed more than 20 worshippers in May 2004.
Gul Hasan had been sentenced to death, but the court agreed with his lawyer's claim that the conviction was flawed. He had already been acquitted over the bombing of another mosque, in which a similar number of people died.