Two Turkish ministers' sons were referred to court Friday for their alleged involvement in a corruption network revealed by the nation's largest ever bribery investigation, private NTV news channel reported. Turkey's Interior Minister Muammer Guler's son Baris Guler and Economy Minister Zafer Caglayan's son Kaan Caglayan were referred to court along with 12 others, according to the report. Nearly 50 people, including some prominent businessmen close to Prime Minister Recep Tayyip Erdogan, and sons of three ministers, were detained Tuesday as part of the probe into alleged tender fraud and bribery. Environment and Urban Planning Minister Erdogan Bayraktar, his son and EU Minister Egemen Bagis, also face corruption allegations. The investigation comes amid a power struggle between the Erdogan's government and an influential U.S.-based Muslim cleric Fetullah Gulen, who has great influence in police and judiciary. Police seized 4.5 million U.S. dollars in cash on Wednesday when they raided the house of Suleyman Aslan, general manager of state-held Halkbank. Opposition parties have called for nationwide anti-corruption protests and demanded dismissal of the ministers whose sons were involved in bribery. However, Erdogan on Wednesday slammed the anti-graft probe as a "dirty operation" with international links to undermine Turkey's economic growth.