In order to survey the compound where Usama bin Laden was hiding, the CIA used a new type of stealth drone to fly dozens of missions into Pakistani airspace undetected, The Washington Post reported Tuesday.

The unmanned planes conducted flights over the compound in Abbottabad, Pakistan for months before the Navy SEALs raid on May 2 that killed the Al Qaeda leader, The Post said, adding that they captured high-resolution video necessary to plan the mission.

The ability to evade radar detection and operate at high altitudes allowed the stealth drones – a model known as the RQ-170 Sentinel -- to travel beyond the normal limits that Pakistan has imposed on other U.S. drones, the paper reported.

A former U.S. official familiar with the operation told The Post that the agency “needed to see more about what was going on” than other surveillance methods allowed. Highly advanced aircraft were just one of many methods used, but their role was made necessary by the location of bin Laden’s compound – near military and nuclear sites with systems that could have detected Predator drones or other non-stealth aircraft.

The use of U.S. drones in Pakistan was already a tense subject between the two countries even before the bin Laden raid.

The U.S. refuses to publicly acknowledge the covert CIA drone program in Pakistan, but officials have said privately that the strikes have killed many senior Al Qaeda and Taliban commanders.

U.S. officials believe Pakistani intelligence continues to support militants who attack U.S. troops in Afghanistan, and actively undermine U.S. intelligence operations to go after Al Qaeda inside Pakistan. The level of distrust is such that keeping Pakistan in the dark was a major factor in planning the raid.

Pakistani officials regularly condemn drone attacks as violations of the country's sovereignty. But many are believed to privately support the program, and some of the drones are suspected of taking off from inside Pakistan.

Continued drone attacks in the weeks following bin Laden’s death are evidence that the U.S. is not letting up on cross-border drone strikes into Pakistan despite complaints that the U.S. violated its sovereignty by killing bin Laden on their soil.

The Associated Press contributed to this report