The prosecution said on Friday it has raided Kumho Asiana Group and Asiana Airlines’ offices to secure documents for its probe into alleged unfair internal transactions.

The group, a large Korean chaebol known for its leisure and construction business, currently stands accused of conducting suspicious internal trading to support its subsidiary Kumho Buslines, of which the owner family has the highest stake.

According to the authorities, Asiana Airlines signed a 30-year contract to sell the airline’s in-flight meal business to Swiss airline caterer Gategroup in 2016, on the condition that it invested in Kumho Buslines.

In August, the Fair Trade Commission slapped a fine of 32 billion won ($27 million) on the group and reported Chairman Park Sam-koo and two other executives to prosecutors over what it saw as a questionable financial expedient.

By Yim Hyun-su (hyunsu@heraldcorp.com)