The flight data and cockpit voice recorders of the South Korean airliner that crashed last month stopped recording four minutes before the disaster, the country's transport ministry said.
The Jeju Air plane crash killed 179 people, making it the deadliest air accident on Korean soil. Two cabin crew members were the only survivors.
Investigators hoped the data from the recorders would provide insight into the crucial moments before the tragedy.
The ministry said it would analyze what caused the “black boxes” to stop recording.
The recorders were initially investigated in South Korea, the ministry said.
When data was found to be missing, it was taken to the US and analyzed by US safety regulators.
The plane was traveling from Bangkok on December 29 when it made an emergency landing at Mueang International Airport and slid into a wall at the end of the runway, bursting into flames.
Sim Jae-dong, a former accident investigator at the transport ministry, told Reuters that the loss of data in the crucial final minutes was surprising and suggested that all power, including the backup, could have been cut.
Many questions remain unanswered. Investigators are looking into the role that bird strike or weather conditions may have played a role.
They also focused on why the Boeing 737-800 had not lowered its landing gear when it hit the runway.