By Hyunjoo Jin and Hyunsu Yim SEOUL (Reuters) -South Korean police said on Thursday they had raided Jeju Air and the operator of Muan International Airport as part of their investigation into Sunday's crash that killed 179 people in the worst aviation disaster on the country's soil.

Officials are inspecting the black boxes recovered from the wreckage of Jeju Air flight 7C2216 and have promised to release updates as soon as possible. The Boeing 737-800 is believed to have suffered a bird strike, but the exact circumstances surrounding its belly landing and subsequent destruction are unclear.

STORY: South Korea stepped up its investigation into its deadliest-ever air disaster on Wednesday.The transport ministry reported that investigators have extracted data from Jeju Air flight 7C2216's cockpit voice recorder and are converting it to an audio file.

The investigation into the Jeju Air plane crash will take several weeks, but some experts say the placement of a concrete barrier at Muan Airport may have played a key role in the deadly aviation disaster.

A South Korean Jeju Air passenger jet crashed on landing at Muan International Airport on Sunday, killing 179 people in the country's deadliest air disaster.

Belly-landings are risky and carried out only in an emergency. Here are the situations in which this is done, and what probably happened with the Jeju aircraft.

On Sunday, 179 people were killed when Jeju Air Flight 7C2216 crashed at Muan Airport after an apparent bird flight caused its front landing gear to malfunction

Maps and diagrams break down the final minutes of Jeju Air flight 2216 that ended in the deadliest air crash in South Korea.

The search warrant lists charges of professional negligence resulting in death after 179 people were killed on a Jeju Air flight.