POSCO shares closed at 238,000 won ($214.60) on the main bourse, down 2.66 percent from the previous session. They dropped to as low as 237,000 won at one point, marking the lowest level in 52 weeks.

The drop comes after Maeil Business Newspaper and other local media reports showed that Berkshire Hathaway unloaded 4.5 percent, or nearly 4 million shares, of POSCO during the second quarter of last year, citing an analysis by a global financial information provider.

Berkshire Hathaway made public in 2007 that it bought a 4.6 percent stake in POSCO and its holding once increased to 5.2 percent. When Buffet visited South Korea in 2011, he reportedly praised POSCO as an "incredible steel company."

No specific reasons were mentioned for the sell-off but the reports cited some market experts who said that Buffet might have lost interest in POSCO due to its deteriorating business condition and performance.

POSCO officials said that they are not capable of confirming the reports because most of Berkshire Hathaway's transactions are done through private equity funds.

Market watchers said that if the reports prove to be true, Buffet might have raked in a profit of between 80 and 110 percent based on his average stock purchasing price of about 150,000 won.

POSCO shares traded in the range of 280,000 won to 320,000 won during the second quarter of last year before rising to as high as 361,000 won in September. They continued to fall thereafter to as low as 242,500 won on Monday.

The news came as POSCO is under pressure from a protracted slump in the global steelmaking industry. POSCO, South Korea's largest steelmaker, posted a nearly 60 percent plunge in net profit last year.

POSCO also has been facing a prosecution investigation into slush fund creation and other corruption allegations. Experts worry that the ongoing group-wide probe could significantly hurt its brand image, possibly having a negative impact on its future business. (Yonhap)