The black boxes holding flight data and cockpit voice recorders of Jeju Air’s Boeing 737-800 jet stopped recording about four minutes before the plane disaster in South Korea in December, the country’s transport ministry has said.

Jeju Air’s Flight 7C2216 was flying from Thailand to Muan International Airport in South Korea on December 29, when it belly-landed, slammed into a concrete barrier and exploded, killing 179 of the 181 passengers and crew.

It was the worst-ever aviation disaster on South Korean soil.

“The analysis revealed that both the CVR and FDR data were not recorded during the four minutes leading up to the aircraft’s collision with the localiser,” South Korea’s transport ministry said on Saturday, referring to the two recording devices.

The localiser is a barrier at the end of the runway that helps with aircraft landings and was blamed for exacerbating the crash’s severity.

The voice recorder was initially analysed in South Korea, and, when data was found to be missing, was sent to a United States National Transportation Safety Board laboratory, the ministry said.

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But it appears that the boxes holding clues to the flight’s final moments experienced data loss, leaving authorities trying to find out what happened.

“Plans are in place to investigate the cause of the data loss during the ongoing accident investigation,” the ministry said.

Sim Jai-dong, a former transport ministry accident investigator, told Reuters news agency that the discovery of the missing data was surprising and suggested all power, including backup, may have been cut in the plane, which is rare.

Investigators said the boxes were crucial to their probe but added they would not give up on trying to find out why the crash happened.

Investigators have pointed to a bird strike, faulty landing gear and the runway barrier as possible issues.

The pilot had also warned of a bird strike before pulling out of a first landing and initiating a go-around.

But instead of making a full go-about, the Boeing 737-800 jet took a sharp turn and approached the airport’s single runway from the opposite end, crash-landing without landing gear deployed.

This week, lead investigator Lee Seung-yeol told reporters that “feathers were found” in one of the plane’s recovered engines, but cautioned a bird strike does not lead to an immediate engine failure.

Authorities have raided offices at Muan airport where the crash took place, a regional aviation office in the southwestern city, and Jeju Air’s office in the capital, Seoul.

They also barred Jeju Air’s chief executive from leaving the country.

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As the probe continues, transport minister Park Sang-woo offered his resignation earlier this week, saying he feels “a heavy sense of responsibility regarding this tragedy”.