A United States F-15 pilot rescued after being shot down above Iran in April reported seeing an unusual “jellyfish” formation of Iranian drones before ejecting, CNN reported on Tuesday, citing sources.

During a post-mission debrief, the pilot reportedly told intelligence officials he observed several drones moving together in a pattern resembling a “jellyfish”, sparking debate within the US intelligence community.

If accurate, the sighting could indicate a significant advancement in Iran’s drone technology, said the report.

One source familiar with the account described it as “multiple drones interconnected and moving as one with smaller drones below the bigger drones like legs.” The source added, “Real alien (expletive).”

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Another source said the pilot saw a “minefield of drones” in the sky, according to the report.

Investigators are still determining what caused the F-15 to be downed, but early assessments suggested the drone formation may have helped Iran shoot down the aircraft, said the report.

The incident marked the first US aircraft shot down above Iran during the conflict. The pilot was recovered within hours, while a weapons systems officer evaded capture for more than one day before being rescued.

US intelligence officials disagreed about the pilot’s account and its reliability, said the report. During the debriefing, officials reportedly asked, “Are you sure you saw what you are saying you saw?”

The questions surrounding Iran’s drone capabilities came as Washington and Tehran pursue negotiations to end the war, following the start of a 60-day ceasefire-based talks period last week.