Pakistani officials have detained a doctor who the U.S. Central Intelligence Agency (CIA) paid to secretly collect DNA samples from Osama bin Laden’s compound, a report said Monday.

Prior to the raid that killed the al Qaeda chief on May 2, the CIA recruited Shakil Afridi, a doctor who works for the the Pakistani government in the Khyber Pakhtunkhwa province, according to McClatchy.

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Through satellite images and operatives in the CIA’s Abbottabad safe house, the agency was able to determine that the tall man living at the compound was probably bin Laden, but they wanted to verify their suspicions.

Afridi was tasked with carrying out an elaborate plot to identify the terrorist leader by collecting DNA from his children through the guise of providing free hepatitis B vaccines. The DNA could then be compared with DNA from bin Laden’s sister, who died in Boston last year.

The doctor traveled to Abbottabad in March and April where he hired local nurses who had previously visited the compound to administer polio drops. Posters advertising the fake hepatitis B vaccinations were posted around the town.

One nurse did reportedly gain access to the compound, but it was unclear if she was successful at gathering any DNA samples.

Reports have said that Pakistan has detained people who were thought to have helped the U.S. gather intelligence on bin Laden, but this is the first time someone has been named. The U.S. is thought to be urging Afridi’s release.

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U.S. officials have been increasingly concerned that Pakistan is more focused on learning how the CIA was able to track down bin Laden than investigating how he was able to hide out in the country for so long.

“Wouldn’t any country detain people for working for a foreign spy service?” one senior Pakistani official asked McClatchy.