Former Israel Navy Commander Vice Adm. (ret.) Eliezer Marom and David Shimron, Prime Minister Benjamin Netanyahu's personal attorney and cousin, are two of six suspects in an alleged graft case involving Israel's defense spending, the Israel Police said Tuesday. The investigation, dubbed Case 3,000, centers on a possible conflict of interest surrounding Israel's 2015 procurement of three submarines and four missile boats from German conglomerate ThyssenKrupp. The Lahav 433 Major Crimes Unit, heading the investigation, interrogated the suspects under caution on Monday. Three suspects -- businessman Miki Ganor, who represented ThyssenKrupp in the deal and is considered the prime suspect in the case; Brig. Gen. (res.) Avriel Bar Yosef, a former deputy head of the National Security Council; and Ronen Shemer, Ganor's right-hand man -- were remanded to custody until the end of the week. Marom and Shimron were remanded to house arrest. The name of the sixth suspect has yet to be released. A police source privy to the investigation stressed that despite the close relationship between Netanyahu and Shimron, the prime minister was not a person of interest in the case. Investigators suspect that Shimron, who represented Ganor in his dealings with ThyssenKrupp, used his relationship with Netanyahu to promote the deal. Shimron was questioned in the case for the third time on Wednesday morning. "Despite a difficult personal and professional situation, to a great extent, Shimron is relieved that he has finally been given the opportunity to present his side of the story in full to law enforcement authorities," Shimron's lawyer, Amit Hadad, said. "Shimron followed the letter of the law and cooperated in full with investigators. He is sure the police will reach the same conclusion, and will make himself available to the investigators whenever they wish." Marom is suspected of fraud, receiving illicit benefits, money laundering and tax fraud. The police allege that during his term as navy chief, Marom conditioned a 2009 submarine deal on a demand that Ganor replace ThyssenKrupp's previous representative in Israel Yeshayahu Bareket, a retired Israeli Air Force officer. The police are also investigating suspicions that Marom abused his position as navy commander and his ties with ThyssenKrupp to ensure that the German company won a tender to build four combat vessels meant to protect Israel's natural gas reserves, in exchange for illicit benefits. Israel Shipyards was also in the running, but lost the tender to ThyssenKrupp. Maron, currently the chairman of the Israel Airport Authority, was questioned for 10 hours on Tuesday, before being placed on house arrest. "I strongly opposed the purchase of a sixth submarine while Miki Ganor represented the [ThyssenKrupp] shipyard, and I sent a letter to that effect to decision-makers," the former navy chief said in a statement. "During my [navy] service I never made even one acquisition involving the shipyard represented by Miki Ganor -- on the contrary. These claims are slanderous. My sole consideration has always been [Israel's] security." Maron's attorney, Zion Amir, issued a statement saying, "I have no doubt that the police investigation will completely debunk all the suspicions allegedly raised against Vice Adm. (ret.) Marom and prove that he has done nothing wrong. He has always contributed to Israel's security, and the investigation will prove that here, too, Marom's involvement only contributed to the State of Israel and did not harm anyone." Follow the money Major Crimes Unit investigators have been able to locate a bank account in Cyprus where large sums of money were deposited in favor of bribed Ganor allegedly paid Maron and Bar Yosef. Ganor, Bar Yosef and Shemer's assets have been frozen as part of the probe while investigators, working with the Israel Tax Authority and the Israel Money Laundering Prohibition Authority, try to trace additional accounts and wire transfers. During Ganor's arraignment before the Rishon Lezion Magistrates' Court, a police official described the investigation as "a very worrying case involving Israel's defense spending to the tune of billions [of dollars]. The investigation raises serious concerns of integrity violations, breach of trust and giving and receiving bribes." Attorney Nati Simchony, who represents Ganor, issued a statement Tuesday: "The investigation was expected, Mr. Ganor cooperated with investigators in full, he intends to provide them with all the information he has, and he believes that it will bring an end to this affair. He is convinced that he has done nothing wrong." Bar Yosef's attorney, Jack Chen, said that "after many months of media reports, Avriel is pleased to have the opportunity to answer questions and refute these allegations." The submarine graft case is not the first time Bar Yosef has come under suspicion. In November 2016 he was questioned on suspicion of bribery, money laundering, fraud and breach of trust in a case involving Israel's offshore natural gas ventures. At the time, Bar Yosef, who served on the steering committee debating Israel's gas exports policy, had a close business relationship with a German businessman involved in gas exports, and was suspected of trying to promote the German businessman's interests in exchange for illicit benefits. Bar Yosef's wife, Aliza, was also questioned in the case. Attorney General Avichai Mendelblit ordered the police to launch a criminal investigation into the submarine deal in February. State Attorney Shai Nitzan had stressed that Netanyahu was not a suspect in the case. At the time, Netanyahu commented on the investigation saying, "The principle guiding me is clear -- Israel will be able to defend itself, by itself, against any enemy. Israel's security requires submarines and the upgrading of the submarine fleet. These are strategic weapons systems that guarantee Israel's very existence."