The Seoul Central District Prosecutors' Office sent its investigators handling immigration affairs to the headquarters of the country's flagship carrier in western Seoul, according to the sources. It was later confirmed that the residence of Korean Air Chairman Cho Yang-ho was not included in the raid.
The move is part of a probe into allegations that Korean Air had been involved in recruiting housekeepers from the Philippines and other countries for Cho's family. Other details related to the suspicion that led to the raid were not known yet.
The investigation will look into the seized documents and records to see if there had been any illegalities in the process.
Authorities are planning to summon Korean Air officials allegedly involved in the case if necessary.
This is the latest in a series of instances of negative media attention being trained on Korean Air and Cho's family.
On Thursday, Cho quit the top post in Jin Air Co., the low-cost carrier unit of Korean Air, amid ongoing investigations into his family over a series of allegations.
In April, South Korea's customs service raided Korean Air headquarters over suspicions that Cho's family members sneaked luxury goods into the country without paying duties. Police have launched an investigation into chairman Cho's wife -- Lee Myung-hee -- over alleged physical and verbal abuse.
Cho's youngest daughter, Cho Hyun-min, a former executive of Korean Air and Jin Air, is also the subject of a probe for allegedly throwing water in the face of an ad agency manager during a meeting in March. (Yonhap)