Pakistan gave China access to the previously unknown US “stealth” helicopter that crashed during the commando raid that killed al-Qaeda leader Osama bin Laden in May despite explicit requests from the CIA not to, the Financial Times reported on Sunday.

The disclosure, if confirmed, is likely to further shake the US-Pakistan relationship, which has been improving slightly after hitting its lowest point in decades following the killing of bin Laden.

During the raid, one of two modified Blackhawk helicopters, believed to employ unknown stealth capability, malfunctioned and crashed, forcing the commandos to abandon it.