Cho Hyun-ah, the infamous "nut rage" heiress to Korean Air Lines Co., was questioned by the immigration office Thursday over fresh allegations that she illegally hired housekeepers from the Philippines.

Cho, the daughter of Hanjin Group Chairman Cho Yang-ho, presented herself at the Seoul office of the Korea Immigration Service just before 1 p.m.

Wearing a blue shirt and cardigan, she stopped briefly in front of a swarm of reporters and camera crews.

"I am sorry for causing trouble," the 44-year-old said in a faint voice, lowering her head.

She faces allegations that she has recruited at least 20 Filipino maids over the past decade by sponsoring them with traineeship visas against the law.

The authorities believe the housekeepers were hired by Korean Air on paper, but in fact worked as maids for Cho and her mother Lee Myung-hee in their Seoul mansions.

It was another inglorious public appearance for the former vice president of Korean Air Lines Co. and heiress to the conglomerate that has businesses ranging from the air carrier to hotels. She was released from jail in May 2015 after the top court suspended her sentence over the 2014 nut rage case.

Cho was convicted of violating the aviation safety law in 2014, as she forced an Incheon-bound flight at New York John F. Kennedy Airport back to the boarding gate and ejected the cabin crew chief because she was angry over the way her macadamia nuts were served.

The Cho family is under intense scrutiny by both public and law enforcement over mounting allegations ranging from abuse of power, assaults and tax evasion to smuggling of luxury goods.

Lee Myung-hee, the chairman's wife, is suspected of involvement in the illegal hiring of foreign maids and will be questioned, the immigration office said. She is also set to be grilled by police next Monday over other assault and abuse allegations. (Yonhap)