From a letter sent to AW owners:
"... Immdeiately after the notification of the event, based on the reported conditions of the aircraft, AgustasWestland started a detailed analysis and a complete review of the Tail Rotor log reports; no aircraft issues were found.
Furthermore, based on the first examination of the recovered aircraft it appears that the incident effects are fully compatible with an external Foreign Object Damage (FOD), which caused a tail rotor imbalance damaging the components of the anti-torque system.
The Flight Data Recorder (FDR) data, recently downloaded, confirm the impulsive characteristc of the phenomenom while the other aircraft parameters appear to stay inside the normal operating ranges. ..."