The recorders were initially researched in South Korea, the ministry said.
When the data was found to be missing, it was brought to the US and analyzed by US security agencies.
The plane was flying from Bangkok on December 29 when it made an emergency landing at Mueang International Airport and crashed 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 news agency that the loss of data in the crucial final minutes was surprising and suggested that all power, including backup power, may have been cut.
Many questions remain unanswered. Investigators looked into the role of this the sound of birds or weather conditions may have played a role.
They also focused on why the landing gear of the Boeing 737-800 did not descend when it hit the runway.
