Jerusalem (CNN) An eighth suspect has been arrested and questioned in a growing corruption probe that has implicated some of Israeli Prime Minister Benjamin Netanyahu's closest confidants.

Eli Kamir -- an Israeli media adviser -- was arrested Sunday morning and questioned "under caution," Israeli police and the Israel Securities Authority said in a joint statement, meaning he is suspected of having committed a crime in the case, known as Case 4000.

Kamir was previously arrested in a fifth case involving those close to the Prime Minister, but he was released from that investigation only to be re-arrested a short time later.

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In court documents, Kamir's lawyer said his client had already given testimony in 2016 in relation to a case involving the Israeli telecommunications company Bezeq and that he was not arrested at the time. His lawyer insisted he had done nothing wrong and that the new case was a means of pressuring him in other investigations. Kamir was released to house arrest.

Israeli tycoon Shaul Elovitch, second from left, appears in the Justice Court in Tel Aviv on Thursday.

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