Detectives from Scotland Yard investigating the death of ex-Pakistani Prime Minister Benazir Bhutto say she died from a severe injury when a bomb blast slammed her head into her vehicle, and not from a gunfire as previously believed, they wrote in a report released by Pakistani’s Interior Ministry Friday.

“The blast caused a violent collision between her head and the escape hatch area of the vehicle, causing a severe and fatal head injury,” said the report, signed by Detective Superintendent John MacBrayne, according to BBC News.

Bhutto’s family, however, rejected the theory as well as Bhutto’s People’s Party. A spokesperson for the party said that British investigators were limited in their investigation and that the party remained convinced that Bhutto died from a gunshot wound, CNN International Reported.

“The party is still looking at the Scotland Yard report- however, it is difficult to agree with its findings on the cause of death. We do believe that she was killed by an assassin’s bullet,” spokesperson Sherry Rehman was quoted by the BBC.

The report is hard to believe, as the British investigation was complicated by the “lack of an extended and detailed search of the crime scene, the absence of an autopsy, and the absence of recognized body recovery and victim identification processes," the report said.

The family refused the autopsy that would have allowed the cause of death to be established more fully.

TV shots from December 27 when Bhutto died, pictured a gunman aiming a weapon at the Pakistani opposition leader as she stood through the sunroof of a vehicle during a rally in Rawalpindi.

Meanwhile, Pakistani authorities said Thursday they arrested two alleged militants they believed to have been involved in Bhutto’s death. The two men were held in a raid in the garrison city of Rawalpindi and were identified only by their single names Rafaqat and Husnain. They provided no details on their role in the attack that led to other 20 deaths.

Last month, Pakistani authorities also arrested a 15-year-old boy in Pakistan’s North-West Frontier Province and a man named Sher Zaman, who alleged to have been involved in the suicide squad assigned to kill Bhutto.

Shah told investigators that Baitullah Mehsud, a prominent Pakistani Taliban militant leader with strong ties to Al-Qaeda, had dispatched a five-person squad to Rawalpindi to kill Bhutto.

The government has already blamed Mehsud for orchestrating the attack. Mehsud has denied any involvement.

Meanwhile, tens of thousands of Bhutto’s supporters gathered outside her tomb in southern Pakistan on Thursday to mark the end of the official 40-day mourning period for their late leader.