A Scotland Yard inquiry in the assassination of Pakistan opposition leader Benazir Bhutto found that she died from the impact of a suicide bombing, not bullets fired at her moments earlier as she left a political rally, a US newspaper reported Friday. British officials were to release a summary later Friday of a report on the probe into Bhutto's Dec. 27 death. The New York Times quoted officials familiar with the report as saying that Scotland Yard investigators concluded she died after hitting her head as she was thrown by the force of the blast. They also determined that the attack was carried out by a single person who blew himself up after opening fire, not by two as authorities had originally reported, the newspaper said. The finding supports the Pakistani government's contention that Bhutto suffered a fatal head wound when she hit her head after the blast. Opponents of President Pervez Musharraf, many of whom suspect a broad conspiracy, have been highly skeptical of that theory, which is seen as minimizing the government's responsibility for a security breach that allowed the gunman to get close to Bhutto. A spokeswoman for Bhutto's party said she was aware of the newspaper account but had not yet seen the full report. She also said the British investigators were limited in their ability to investigate the killing fully and that as a result the party remained convinced that Bhutto died of a gunshot wound. "Their terms of reference were limited," spokeswoman Sherry Rehman said of the British probe. "They were working under the Pakistani police. Their investigation was limited only to finding the cause of her death." Police arrested two more suspects Thursday in the assassination, as thousands of her followers gathered at her tomb to mark the end of mourning and relaunch her party's campaign for this month's parliamentary elections. Interior Ministry spokesman Javed Iqbal Cheema said the two suspects in the killing were picked up in Rawalpindi, where Bhutto was killed. They appeared Friday before an anti-terrorism court in Rawalpindi and were ordered held for at least 12 more days, officials said. Cheema declined to say whether the two men were key figures in the assassination. "I can't really comment on whether (the arrest) is important," Cheema told The Associated Press. "After the investigation, I will be in a position to say more." Last month, police in northwestern Pakistan arrested two other suspects, including a 15-year-old boy who was alleged to have been part of a backup suicide squad assigned to kill Bhutto if the primary assassins failed. A security official, speaking on condition of anonymity because of the sensitivity of the information, said the latest suspects were picked up based on information provided by the first two. Musharraf invited Scotland Yard to conduct its own inquiry after Bhutto supporters alleged the government may have been involved in her death. Musharraf rejected calls from Bhutto's party for an independent UN investigation. US and Pakistani officials believe the assassination was masterminded by Baitullah Mehsud, an al-Qaida-linked commander based in South Waziristan. Mehsud leads Tehrik-e-Taliban Pakistan, a coalition of Islamic extremist groups fighting Pakistani forces in the lawless tribal area along the border with Afghanistan. On Wednesday, Mehsud's coalition announced an indefinite cease-fire with Pakistani forces. Bhutto's slaying triggered nationwide riots that caused billions of dollars (euros) in damage and the deaths of at least 40 people. That prompted the government to postpone parliamentary elections for six weeks until Feb. 18. The balloting is aimed at restoring civilian government after eight years of military rule. Musharraf was re-elected president in October but needs a strong majority in Parliament to fend off growing demands for his impeachment. Although the stakes are high, there has been little sign of public enthusiasm for the elections. Campaigning virtually stopped after Bhutto's death, in part out of respect for the traditional 40-day mourning period and also over fears that Islamic extremists would attack large public gatherings. However, Bhutto's Pakistan People's Party said it was ready to resume the campaign following the end of the mourning period. The party, now led by her husband, Asif Ali Zardari, plans a major rally Saturday.