Prosecutors are poised to question top executives of Livedoor Co., including President Takafumi Horie, over alleged fraudulent practices apparently designed to expand the firm's business, investigative sources said Thursday.

The Internet and financial services conglomerate is at the center of a high-profile probe being conducted by the special investigative squad of the Tokyo District Public Prosecutor's Office.

Reports that the squad raided the company's headquarters and Horie's home, both in Tokyo, and other places Monday night sparked a massive selloff Tuesday and Wednesday on the Tokyo Stock Exchange that forced the bourse to close Wednesday's trading early.