Effi Naveh, a member of the committee that appoints judges, appeared in court for an extension of his arrest in a case that has rocked the country's legal system.
Police spokesman Micky Rosenfeld said the Lahav 433 investigative body was looking into "offenses of integrity" regarding attempts to appoint two judges. He said police have seized documents as part of the investigation.
Police could not be reached for comment on the media reports about his arrest, which dominated the evening news.
Israeli media say Naveh is accused of breach of trust and accepting bribes, and ran reports of his sexual relations with two women who were candidates for judgeships, allegations Naveh has reportedly denied.
Israeli media reported that Israel's attorney general recused himself from the case because of his friendship with the main suspect and that the country's justice minister and chief justice of the Supreme Court will be called to testify.