Investigators found bird feathers and blood in both engines of the Jeju Air jet that crashed in South Korea last month, killing 179 people, a person familiar with the probe told Reuters on Friday.

The Boeing 737-800 plane, which departed from the Thai capital Bangkok for Muan county in southwestern South Korea, belly-landed and overshot the regional airport's runway, bursting into flames after hitting an embankment.

Only two crew members at the tail end of the plane survived the worst aviation disaster on South Korean soil.

About four minutes before the fatal crash, one of the pilots reported a bird strike and declared an emergency before initiating a go-around and attempting to land on the opposite end of the runway, according to South Korean authorities.

Two minutes before the pilot declared the Mayday emergency call, air traffic control had urged caution due to "bird activity" in the area.

Investigators this month said feathers were found on one of the engines recovered from the crash scene, adding that video footage showed there was a bird strike on an engine.

South Korea's transport ministry declined to comment on whether feathers and blood were found in both engines.

The plane's two black boxes - key to finding out the cause of last month's crash on the jet - stopped recording about four minutes before the accident, posing a challenge to the ongoing investigation.

Sim Jai-dong, a former transport ministry accident investigator, said on Sunday the missing data was surprising and suggested all power, including backup, may have been cut, which is rare.

Bird strikes that impact both engines are also rare occurrences in aviation globally, though there have been successful cases of pilots landing the plane without fatalities in such situations including the "Miracle on the Hudson" river landing in the U.S. in 2009 and a cornfield landing in Russia in 2019.