The site of the Jeju Air plane crash is seen in the photo taken from Muan International Airport in Muan County, South Jeolla Province, Dec. 30. Yonhap

Questions have grown over the existence of a concrete mound at the airport of the Jeju Air plane crash this week and whether its absence could have prevented the accident's high number of casualties.

On Sunday, the Jeju Air plane made a belly landing at Muan International Airport in the southwestern county, 288 kilometers south of Seoul, before it overran the runway and exploded as it crashed into the mound, killing 179 of the 181 people on board.

The concrete structure in question holds a navigation system that assists in aircraft landings, known as a localizer, and is located about 250 meters from the end of the runway.

The 2-meter tall structure is covered with dirt and including the localizer, it is 4 meters high. The mound is known to have been built as the localizer was replaced last year.

Airport officials said the mound was raised to keep the localizer level with the runway to ensure it functions properly as the ground at the end of the runway is slanted.

Some experts and observers have raised questions over the mound and whether more lives could have been saved if it was not there as the aircraft skidded about 1,600 meters on the runway before colliding with the structure.

"I've seen many antennas in many airports but it's the first time I've seen such a type," a pilot who requested anonymity said, referring to the localizer. "Even if you want to make the antenna taller, there is no need to build a concrete wall."

The transport ministry has said in briefings that the localizer is installed about 251 meters off the runway and that some other airports in the country also have the equipment installed with concrete structures.

It has also pointed to other airports overseas that have used concrete for such structures.

Authorities are currently investigating the exact cause of the accident.

The remains of 141 of the 179 people killed in the crash have tentatively been identified, according to the transport ministry. (Yonhap)