South Korea's government said on Monday it will extend the shutdown of Muan International Airport by a week to Jan. 14, citing the ongoing investigation into the crash of a Jeju Air jet that killed 179 passengers on board.

Police in South Korea have raided the airport of Muan following a deadly plane crash on site that killed almost all passengers aboard the aircraft last weekend, the Yonhap news agency reported Monday.

Authorities also raided the regional aviation office in Muan, part of Busan’s aviation administration. Read also: Black box data recovered in South Korea’s deadliest plane crash; another sent to U.S.