SEOUL, Jan 27 (Reuters) - South Korea's authorities

investigating last month's Jeju Air plane crash have

submitted a preliminary accident report to the U.N. aviation

agency and to the authorities of the United States, France and

Thailand, an official said on Monday.

The investigation into the deadliest air disaster on the

country's soil remains ongoing, the report made available on

Monday said, focused on the role of "bird strike" and involving

an analysis of the engines and the "localiser" landing guidance

structure.

"These all-out investigation activities aim to determine the

accurate cause of the accident," it said.

The International Civil Aviation Organization (ICAO), the

U.N. agency, requires accident investigators to produce a

preliminary report within 30 days of the accident and encourages

a final report to be made public within 12 months.

The Boeing 737-800 jet, from Bangkok and scheduled to

arrive at Muan International Airport, overshot the runway as it

made an emergency belly landing and crashed into the localiser

structure, killing all but two of the 181 people and crew

members on board on Dec. 29.

The localiser aids navigation of an aircraft making an

approach to the runway, and the structure built of reinforced

concrete and earth at Muan airport supporting the system's

antennae was likely a cause of the disaster, experts have said.

The report highlighted much of the initial findings by the

South Korean investigators that was shared with the families of

the victims on Saturday, including the pilots discussing a flock

of birds they spotted on its final approach.

The exact time of a bird strike reported by the pilots

remains unconfirmed, the accident report said, but the aircraft

"made an emergency declaration (Mayday x 3) for a bird strike

during a go-around."

"Both engines were examined, and feathers and bird blood

stains were found on each," it said.

"After the crash into the embankment, fire and a partial

explosion occurred. Both engines were buried in the embankment's

soil mound, and the fore fuselage scattered up to 30-200 meters

from the embankment," it said.

The report does not say what may have led to the two data

recorders to stop recording simultaneously just before the

pilots declared mayday. The aircraft was at an altitude of 498

ft (152 metres) flying at 161 knots (298 km/h or 185 mph) at the

moment the blackboxes stopped recording, it said.