South Korea's crackdown on the family-run business empires - known as chaebols - continues with the chairman of SK Group being summoned for questioning over alleged illegal stock deals.
Son heads the third biggest business group in South Korea
South Korea's new President Roh Moo-hyun is leading a drive to break the chaebol's grip on the economy.
The chaebol's internal business deals have been blamed for the country's financial crisis in 1997, when it was bailed-out by the International Monetary Fund to the tune of $58bn.
On Tuesday, the Fair Trade Commission announced it would launch an inquiry into alleged illegal business practices by the five biggest chaebols, including SK, Hyundai and Samsung.
The summons for SK Group's chairman Son Kil-seung
comes after the arrest of the chairman and president of subsidiary SK Corp, the country's largest oil refiner, for unrelated allegations of illegal stock deals.
Mr Son's inquires related to his role in SK Global, the group's trading arm, buying securities from JP Morgan at inflated prices to settle a dispute with the US bank.
SK Global is also accused of manipulating its accounts.
The summons follows raids by the South Korean prosecutors on SK Group's offices.
Mr Son is also head of the Federation of Korean Industries lobby group.