The National Tax Service(NTS) is conducting a tax investigation against private equity firm MBK Partners, which is the largest shareholder of retail giant Homeplus.

According to industry sources on Tuesday, the NTS Seoul Regional Office launched the probe earlier in the day.

MBK Partners explained that the investigation is a regular inspection conducted once every four to five years.

There is, however, speculation that the Seoul tax office may expand the scope of the probe in consideration of the liquidity situation surrounding Homeplus.

After acquiring Homeplus in 2015 with a large amount of loan, MBK Partners has focused on paying off debt and payback through store sales and receiving dividends.

Before applying for Homeplus' court rehabilitation process, its largest shareholder sold commercial paper(CP) to its investors.