Investigators are yet to establish why a helicopter involved in a crash which killed the owner of Leicester City lost control.
Before the AW169 helicopter spun out of control it turned right, despite the pilot's left pedal command, according to a preliminary report by the Air Accidents Investigation Branch (AAIB).
The AAIB stated that the "cause of the apparent loss of yaw control has yet to be determined" but revealed that "investigation of the tail rotor system is being carried out as a priority".
Footage of the incident appears to show that sections of the tail rotor may have fallen off in mid-air.
The aircraft reached an altitude of approximately 430ft before plummeting to the ground near Leicester City's King Power Stadium, the AAIB said.
It was "rapidly engulfed in an intense post-impact fire" and all five people on board were killed.
Leicester City owner Vichai Srivaddhanaprabha, employees Nursara Suknamai and Kaveporn Punpare, pilot Eric Swaffer and his partner, Izabela Roza Lechowicz - who was also a professional pilot - were all killed in the accident on October 27.
