Police investigators questioned Benjamin Netanyahu Friday morning at the Prime Minister’s Residence in Jerusalem in the Bezeq corruption probe, a day before he is set to embark on a week-long diplomatic trip to the United States.

The Ynet news site reported that the prime minister and his wife, Sara, were questioned under caution as suspects in the case. Police said only that the couple “were questioned for a number of hours as part of an investigation” by police and the Israel Securities Authority.

It had also been expected that Netanyahu would be questioned in Case 3000, which involves suspected corruption in the multi-billion-shekel purchase of submarines and other military naval vessels from a German shipbuilder. But police investigators did not in the end touch on the matter in Friday’s session.

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While police were speaking to Netanyahu, his wife was interrogated separately for five hours at the Lahav 433 anti-corruption unit’s headquarters in Lod as part of the Casse 4000 probe. Interrogators reportedly informed her that she was also a suspect in the case.

Asked to confirm which cases the questioning referred to and whether the prime minister or his wife were being treated as criminal suspects, a police spokesman remained vague, telling The Times of Israel only that the interrogations took place “in general as part of the investigation.”

“There are no further details or information on the ongoing investigations,” the police added.

The Attorney General’s Office, which usually authorizes the decision to treat a public official as a criminal suspect, declined comment on the questioning. Police however confirmed that it was “being carried out with the supervision of the state attorney and approval of the attorney general.”

At the same time as questioning Benjamin and Sara Netanyahu, police also brought in suspects Shaul Elovitch and Nir Hefetz for another round of questioning in the case, and also interrogated a former official at the Communications Ministry.

The Bezeq case, also known as Case 4000, involves suspicions that Elovitch, chief shareholder of telecommunications giant Bezeq, ordered the Walla news site, which he also owns, to grant fawning coverage to the Netanyahus in exchange for the prime minister’s advancement of regulations benefiting him.

Speaking at a hearing this week regarding Elovitch and Hefetz — a former media adviser for the prime minister who has also been implicated in the case — state prosecutor Yehudit Tirosh of the Israel Securities Authority said that Netanyahu was at the center of “a very grave instance of giving and taking bribes.”

Questioning the two at the same time allows investigators to present identical material to both, including recordings and text messages gathered during the probe.

Arguing Tuesday against releasing Elovitch and Hefetz from police custody, Tirosh said that state prosecutors believed they would try to obstruct the investigation, even possibly suggesting illicit consultations with Netanyahu himself.

“There is a real suspicion that if the suspects are released today, hugely important investigative work that needs to be carried out in the coming days will be thwarted,” she said.

With Hefetz and Elovitch still in police custody, they would not have had the opportunity to speak with Netanyahu before he faced police.

Investigators are in possession of correspondence between Sara Netanyahu and Elovitch’s wife that appear to implicate the prime minister’s wife in the burgeoning scandal, Channel 10 news reported Thursday.

Earlier in the week, the news outlet published a text message sent by Sara Netanyahu to Iris Elovitch, the Bezeq owner’s wife, blasting coverage of the Netanyahus on Walla and urging her to “quickly” change it.

“You’re killing us. You’re slaughtering us. You’re destroying the state. What type of site is this?” Sara Netanyahu wrote in a WhatsApp message at an unspecified time, according to the report. “Change this. Do something with this. You’re the owners of the site. This should happen quickly.”

In another text, Netanyahu reportedly asked Elovitch why Walla editor Aviram Elad had not yet been fired.

“It can’t go on like this, I thought we talked about this. This has gone on too long. Why do I need to read on your website about things like this? Do something about this!” Sara Netanyahu wrote in the message.

Iris Elovitch, who is herself a suspect in the case, criticized the publication of the first WhatsApp message at the time.

“This is a prohibited and serious leak that distorts reality, while systematically ignoring important facts that weren’t presented [that] would prove that Iris Elovitch didn’t commit any offense,” she said in a statement.

The prime minister, who denies wrongdoing in any of the various corruption cases swirling around him, also slammed “biased and deceptive leaks” in response to the report.

A flurry of developments were reported recently in Case 4000, following the arrest of a number of figures involved in the investigation.

Shlomo Filber, the former director-general of the Communications Ministry and a longtime Netanyahu confidant, signed a deal last week to turn state’s witness and possibly incriminate Netanyahu in the affair.

Filber had his remand extended on Wednesday by 15 days, and is to stay during that time at a facility in an undisclosed location while police continue questioning him.

On Friday, police announced that they had arrested an unnamed former high-ranking official in the Communications Ministry in connection with the investigation.

Netanyahu served as communications minister from November 2014 to February 2017. During that time, Walla’s coverage notably changed to favor the Netanyahu family, and Bezeq was given permission, among other things, to buy the satellite cable provider Yes, overriding antitrust issues, and to renege on its commitment to lease out its infrastructure to other telecom companies so they could provide competing fixed line and internet services.

Sources close to Netanyahu, who himself has denied any wrongdoing in the case, rejected claims that the prime minister had sought to help Bezeq as part of a quid pro quo deal.

“The claims against Prime Minister Netanyahu are baseless. All of the decisions were made for relevant reasons and are based on professional opinions, committees and legal advice,” the sources said on Monday.

Last month, police recommended that the prime minister be indicted for a series of serious corruption charges including bribery, fraud, and breach of trust in two other cases.

In Case 1000, Netanyahu and his wife are suspected of receiving illicit gifts from billionaire benefactors, amounting to some NIS 1 million ($282,000) worth of cigars and champagne from the Israeli-born Hollywood producer Arnon Milchan and Australian resort owner James Packer in return for certain benefits.

Case 2000 involves a suspected illicit quid-pro-quo deal between Netanyahu and Yedioth Ahronoth newspaper publisher Arnon Mozes that would have seen the prime minister weaken a rival daily, the Sheldon Adelson-backed Israel Hayom, in return for more favorable coverage from Yedioth.

Netanyahu denies any wrongdoing.

Times of Israel staff contributed to this report.