South Korean authorities have released a preliminary report on last month's deadly Jeju Air plane crash. It says that feathers and bird blood stains were found in both engines.

The Aviation and Railway Accident Investigation Board on Monday released the initial report, which is intended for submission to an international organization.

The low cost carrier's plane burst into flames after it made a belly landing at Muan Airport in the country's southwest on December 29th, killing 179 people aboard.

Investigators had already found that the plane's flight and cockpit voice recorders had stopped recording almost simultaneously about four minutes before the crash.

According to the latest report, the recordings stopped when the plane was about two kilometers from its originally planned landing point, while it was descending.

Investigators are unsure when a bird strike happened. South Korean media outlets reported that a power failure may have occurred after a bird strike knocked out the engines.

According to the report, after the pilot issued a Mayday call and told ground control that it was to make a second landing attempt, the plane began its ascent. The aircraft then attempted to land from the opposite end of the runway but crashed.

Experts say it will likely take more time to get to the bottom of what happened due to insufficient data from the recorders.