Seoul police on Monday launched a probe into whether the wife of Korean Air's chairman illegally abused employees -- the latest accusation against a powerful, wealthy family with members known for their tantrums.
The hot-tempered clan landed in hot water earlier this month after chairman Cho Yang-ho's second daughter was accused of throwing water into an advertising agency manager's face in a fit of rage during a business meeting.
That came after her sister made global headlines in 2014 for angrily kicking a cabin crew member off a plane after being served macadamia nuts in a bag rather than a bowl.
The incident was dubbed "nut rage", prompting the sister's case to be described as "water rage".
In the latest instalment, police said Monday they were looking into whether the sisters' mother Lee Myung-hee had herself abused employees verbally and physically.
Media reports accused Lee, who is in her late 60s, of a litany of abuse of multiple workers renovating her home and of Korean Air employees, including screaming, cursing, slapping and kicking.
"We have launched a preliminary probe into suspicions that Lee... assaulted and verbally abused multiple people," Yonhap news agency quoted an unidentified police official as saying.
The Cho family saw their homes raided by customs officials over the weekend after media reports emerged that they had smuggled expensive liquor or luxury items using Korean Air flights to evade taxes.
Chairman Cho apologised on Sunday for the "immature" behaviour of his daughters and said they would both immediately resign from their company posts.
The move did little to assuage public fury, with nearly 90,000 people signing an online petition urging the government to ban the firm from using "Korean" in its name.
The 2014 "nut rage" incident saw the older sister Cho Hyun-ah, then the firm's vice president, force two flight personnel to kneel and beg for forgiveness on a Seoul-bound flight from New York before ejecting one of them from the plane before takeoff.
The incident was one of the most infamous cases involving the offspring of South Korea's wealthy business elite, whose arrogance and bad behaviour regularly make headlines.
Cho was jailed but returned to work as an executive at Korean Air's hotel unit in March.