Lee Sun-ho, the 29-year-old son of CJ Group Chairman Lee Jay-hyun, walked into the office alone on Wednesday evening, the Incheon District Prosecutors' Office said in a statement on Wednesday.

Lee was stopped on arrival at Incheon International Airport from the United States on Sept. 1 on suspicion of trying to smuggle marijuana into the country, local media reported citing the prosecutor's office.

Reuters calls to the prosecutors' office seeking details of the allegations went unanswered on Thursday.

In a statement issued by CJ Group on Thursday, Lee apologised "for causing significant trouble to CJ executives and employees and disappointing many people through wrongdoing".

CJ Group in the statement said Lee told investigators he would "take responsibility for his wrongdoing".

On Wednesday, prosecution officials raided Lee's house as part of its investigation, a person familiar with the matter told Reuters.

"The suspect ... said it is heartbreaking that the people around him are suffering and wished to be arrested as soon as possible," the prosecutors' office said in its statement.

Lee, a graduate of Columbia University in the United States, is a business planning executive at food company CJ Cheiljedang Corp, part of the CJ Group which owns movie and entertainment firm CJ ENM Co Ltd as well as CJ Logistics Corp.

The group's leader, Lee Jay-hyun, is a grandson of Samsung Group founder Lee Byung-chull.

(Reporting by Joyce Lee and Hyunjoo Jin; Editing by Christopher Cushing)