As the criminal investigation into Prime Minister Benjamin Netanyahu’s alleged corruption deepened, his office on Wednesday reminded civil servants of the rules prohibiting public officials from accepting gifts and other benefits.

The directive from the PMO’s Human Resources Department instructed employees of government ministries to refamiliarize themselves with the rules regarding receiving gifts, warning it could be prosecuted as a criminal offense.

The email from the department’s Deputy Director Adina Dror included a 2014 memo from the Civil Service Commission outlining the official rules, and emphasized that accepting gifts, even “within the framework of celebrations and family events” was prohibited.

Dror’s email also attached a 2013 update of the 1979 civil service law banning the acceptance of gifts. It was addressed to the Prime Minister’s Office and various government ministries.

“Public officials are forbidden to accept gifts, except according to the conditions set in law and the civil service regulations,” Dror’s message said, quoting the text of the 1979 law. “The purpose of the gift law is to ensure the integrity of public service. It is designed to strengthen the public trust in government authorities.”

“The foundation of the law establishes general guidelines for the expected behavior for public servants, and establish broader guidelines covered by laws regarding bribery and breach of trust,” the memo said.

Prime Minister Benjamin Netanyahu toasts outgoing director of Mossad Tamir Pardo (L) and his successor Yossi Cohen, at a ceremony in Tel Aviv, on January 06, 2016. (Kobi Gideon / GPO)

Prime Minister Benjamin Netanyahu toasts outgoing director of Mossad Tamir Pardo (L) and his successor Yossi Cohen, at a ceremony in Tel Aviv, on January 6, 2016. (Kobi Gideon/GPO)

Dror said the message was sent out “in light of recent events.”

The prime minister has been questioned by police twice in the past two weeks over two separate corruption cases, one of which involves allegations that a number of businessmen have given Netanyahu and his wife, Sara, lucrative gifts during his years in office.

Police have seized receipts for gifts worth up to NIS 400,000 ($104,000) given to Netanyahu by Israeli Hollywood producer Arnon Milchan, during a raid on his Ramat Gan offices, Channel 10 news reported earlier this week.

Last week, Channel 2 news reported that Milchan was one of up to four businessmen eyed as suspected benefactors of the Netanyahus. Milchan is alleged to have provided the prime minister with a steady supply of expensive cigars and his wife with champagne for nearly a decade.

The TV station has also reported that Netanyahu had asked US Secretary of State John Kerry three times in 2014 to intervene on behalf of Milchan and arrange a long-term visa for Milchan to live in the United States. The visa was arranged.

On Sunday, Channel 10 said that in addition to Milchan, Australian billionaire James Packer was also paying for meals for the Netanyahus at their private residence in Caesarea, as well as cigars and champagne. Packer and Milchan are friends and have mutual business interests.

Netanyahu is also under investigation for an alleged quid pro quo deal he arranged with Yedioth Ahronoth publisher Arnon Mozes in 2014.

Police reportedly have recordings of the two discussing the deal, that would have seen the prime minister work to reduce the circulation of the pro-Netanyahu Israel Hayom daily newspaper. In exchange for pushing a bill to require the free daily to have a cover charge, Netanyahu would enjoy more favorable coverage in Yedioth.

The prime minister has repeatedly denied any wrongdoing, and his lawyer has insisted Netanyahu has done nothing illegal.

His spokesperson declined a request Tuesday from the Times of Israel to comment on the latest reports over the receipts or on whether the prime minister had initiated the meetings with Mozes.

Times of Israel staff contributed to this report.