President Lee Myung-bak’s son, Si-hyung, returned home Thursday night after 14 hours of questioning as a criminal suspect by investigators working for an independent counsel. In a new investigation into a property scandal involving the president and his family, the independent counsel is set to summon the president’s older brother, Lee Sang-eun, for questioning soon.

The widening investigation is juxtaposed against an earlier decision by the prosecution to file criminal charges against none of those involved in the case. In clearing them of criminal suspicions in June last year, the top prosecutor in charge claimed that no further investigation was needed because all facts came to light.

But new findings and allegations are strengthening the belief that the prosecution did a shoddy job deliberately after making a decision not to delve deep into an allegation that President Lee, his son and some others breached the law when the president bought plots of land for his retirement home.

The law on property transactions bans a proxy from signing a contract on behalf of the real purchaser, but the president bought the land in his son’s name. The president’s son reportedly made a statement to that effect in his written testimony to the prosecution. But the prosecution did not summon him for follow-up questioning though he was suspected of breaching the property transaction law.

The president’s son borrowed 600 million won from his uncle, reportedly all in cash. He also borrowed another 600 million won from a bank, offering his mother’s property as security. To make the matter even more complicated, the presidential security service bought the land together with the president’s son for the construction of a building for its detail in the complex. An illicit gain was allegedly made for the president’s son in the process.

Lee Sang-eun fanned suspicions about his role in the land purchase when he went out of the country on an alleged business trip on Oct. 16, one day before the independent counsel started his investigation. He was suspected of attempting to dodge an impending investigation. When he returned home on Wednesday, it was not clear whether he did so on his own or under mounting pressure from the independent counsel.

One enigma about him is why he chose the cumbersome way of lending the money in cash, instead of simply transferring it from his bank account to that of his nephew. He will have to answer this question, as well as other questions about his deal with his nephew, when he is summoned by the independent counsel.