Tax authorities have launched a special probe into large-scale private learning institutions as the presidential office has suggested considering judicial action against the country's private education cartels if necessary.

The National Tax Service on Wednesday sent investigators to the head office of MegaStudy, a leading company engaged in the online education business, in Seoul. 

An official of the private education sector said Wednesday marked the first time for the tax agency to conduct a special probe into such institutions since the Lee Myung-bak administration which ran from 2008 to 2013. 

Insiders of the private education sector believe the agency’s probe targeted large-sized institutions, called “hagwon” in Korean,” including those which enjoyed significant growth in recent years. 

Tax authorities are likely to closely look for any illegalities in such institution’s earnings structure and possibility of tax evasion. 

The latest inspection also comes as the private education sector is likely to have expanded their businesses by excessively using the so-called “killer questions” in state-administered university entrance exams as their selling point.