The two flight recorders on board a South Korean airliner stopped working before the jet crashed during an emergency landing and subsequent crash that killed 179 of the 181 people on board, officials said Saturday.

The missing data deepens the puzzle of what caused the deadly air disaster in Muan, South Korea, late last month.

South Korea Eyes Changes As Jeju Air Crash Probe Continues is published in Aviation Daily, an Aviation Week Intelligence Network (AWIN) Market Briefing and is included with your AWIN membership. Already a member of AWIN or subscribe to Aviation Daily through your company? Login with your existing email and password

The two black boxes on the Boeing jet involved in the worst aviation disaster on South Korean soil stopped recording about four minutes before the accident, the transport ministry said on Saturday. South Korean investigators previously said the flight data and cockpit voice recorders were key to finding out the cause of last month's crash that killed 179 people.

South Korea’s leading low-cost carrier, heavy with debt and its stock already near record lows, is now facing intense public and government scrutiny.

South Korea said it planned to improve the structures housing the antennas that guide landings at its airports this year after December's fatal crash of a Jeju Air plane, which skidded off the runway and burst into flames after hitting such a structure.

The black boxes holding the flight data and cockpit voice recorders for the crashed Jeju Air flight that left 179 people dead stopped recording four minutes before the disaster, South Korea's transport ministry said Saturday.