Four program directors and staff members of MBC's Investigative program "PD Notebook" have been arrested on suspicion of intentionally misinterpreting information on U.S. beef to undermine the government's decision to resume imports last June.

The program is believed to have played a major role in triggering massive candlelight rallies against the resumption of U.S. beef imports. The latest round of investigation is the first time the prosecution has looked into the PD Notebook case since prosecutor Lim Soo-bin resigned in January, saying he found the program's "manipulation" intolerable.