SEOUL (REUTERS) - South Korean prosecutors searched Samsung Securities' head office as part of their investigation into the brokerage's recent fat finger error.

The brokerage's accidental issuance of 2.8 billion shares to employees - more than 30 times the number of its outstanding shares and theoretically worth some US$100 billion (S$133.95 billion), prompted a public outcry, particularly after it was discovered that some workers quickly sold off shares.

The country's financial watchdog said this month it had found that 21 employees traded or attempted to sell shares to make a profit from the error and reported them to prosecutors.

The company official confirmed the raid, but declined to provide further details as the investigation is still underway.

A Seoul prosecutor official was not immediately available for comment.

After the error, Samsung Securities promised to rebuild its internal control process and set up a fund to support investors damaged by financial accidents.

Shares in the brokerage were little changed on Monday morning (May 28).