The CIA set up a fake vaccination initiative in the months leading up to the killing of Osama bin Laden, in an attempt to obtain DNA samples from members of his family.
The elaborate scheme was carried out in the town of Abbottabad in Pakistan, where the CIA believed the al-Qa'ida leader was hiding, in an attempt to provide evidence that the family was present in the town, an investigation by The Guardian has revealed.
It was hoped doctors would be able to obtain the DNA of a Bin Laden family member, who the CIA suspected of living in the compound with him, and compare it to a sample from his sister.
The operation was launched after American intelligence officers tracked an al-Qa'ida courier, known as Abu Ahmad al-Kuwaiti, to the compound where Bin Laden was eventually killed.
CIA agents recruited a senior Pakistani doctor to carry out a vaccination drive in the town, which would act as a cover for retrieving the DNA.
The doctor, Shakil Afridi, launched the vaccination programme in March in Nawa Sher, a poor neighbourhood on the edge of Abbottabad, according to Pakistani and US officials and local residents. Mr Afridi, who had previously been the health official in charge of Khyber, part of the tribal area that runs along the Afghan border, had posters advertising the vaccination programme put up around Abbottabad.
Mr Afridi told locals that he had received funds to give free vaccinations for hepatitis B, the newspaper reported. He then paid local government officials and health workers to take part in the operation, unaware of true aim of the project.
It is not known whether the operation succeeded, but one source cited in the report suggests that it did not.
The doctor, Shakil Afridi, has since been arrested by Pakistan's Inter-Services Intelligence (ISI) agency for co-operating with US intelligence officials.
Pakistan's ISI has also arrested five CIA informants who fed information to US intelligence before the raid, according to US officials.
Sixteen people, including Bin Laden's three wives and several children, were de- tained by Pakistani security forces after the US Navy Seals raid.
Relations between Washington and Islamabad, which were already very strained after CIA contractor Raymond Davis killed two Pakistanis in the city of Lahore, worsened significantly following the raid.
The United States kept Islamabad in the dark about the operation until after it was completed, humiliating Pakistan's armed forces and putting US military and intelligence ties under serious strain.