ZAGREB, Jan 20 (Hina) - Six executives of the Podravka company suspected of wrongdoing, who have been in custody since late October, are to remain in custody for two more months. A Zagreb County Court investigating judge decided Wednesday to keep them in detention to prevent possible witness tampering. The ruling can be appealed. Some 50 witnesses have been questioned in the ongoing investigation in the case, and around 20 remain to be heard.