LONDON—A British police investigation into the leak of confidential diplomatic memos is raising press freedom issues, as police warned Saturday that U.K. media outlets might face a criminal inquiry if leaked documents are published.

The Metropolitan Police Counter Terrorism Command is investigating the leak of private memos written by Britain’s ambassador to the United States that were published in the Mail on Sunday six days ago.

The leak led to Wednesday’s resignation of British Ambassador Kim Darroch, who had criticized President Donald Trump in the leaked confidential cables. Trump said his administration would no longer work with Darroch.

British police indicated Saturday they issued the unusual warning because of concerns that more leaked memos are “in circulation.” They say they want editors to know publishing them may be against the law because there is a criminal investigation underway into whether the original leak violated the Official Secrets Act.

The statement appeared timed to prevent Sunday newspapers from publishing more leaked memos.

“The publication of these specific documents, now knowing they may be a breach of the OSA, could also constitute a criminal offence and one that carries no public interest defense,” said Neil Basu, who heads the investigation as chief of counter-terrorism unit. “We know these documents and potentially others remain in circulation.”

British officials say they believe the leak was not a result of outside hacking but seems to have been carried out by an insider. The Foreign Office criticized the leak but did not challenge the authenticity of the memos, which characterized the Trump administration as chaotic and inept.

Darroch’s defenders said his critical memos showed he was doing his job by providing candid assessments, as diplomats are expected to do, but he said the controversy had made it impossible to fulfill his duties.

The Official Secrets Act prohibits public servants from making “damaging” disclosures of classified material. It is aimed at civil servants and others in the government with access to sensitive information and is not designed to target journalists.

Foreign Secretary Jeremy Hunt, who is jousting with Boris Johnson to become Britain’s next prime minister, tweeted Saturday that the person responsible for the leak must be found and held responsible, but he differed with police over whether the publication of leaks is a possible crime.

“I defend to the hilt the right of the press to publish those leaks if they receive them & judge them to be in the public interest: that is their job,” he said in a tweet.

Johnson, a former foreign secretary, also said it would be wrong to seek criminal charges against the press for publishing leaked material.

“A prosecution on this basis would amount to an infringement on press freedom and have a chilling effect on public debate,” Johnson said at a campaign event Saturday.

The Mail on Sunday, which first obtained the trove of leaked memos, has not faced any legal repercussions for its decision to publish.

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Follow AP’s full coverage of Brexit and the Conservative Party leadership race at: https://www.apnews.com/Brexit

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