THE National Enquirer kept a safe containing documents on hush-money payments and other damaging stories it killed as part of its cozy relationship with Donald Trump leading up to 2016 presidential election, people familiar with the arrangement said.

The detail comes as several media outlets reported that federal prosecutors have granted immunity to National Enquirer chief David Pecker, potentially laying bare his efforts to protect his longtime friend Mr Trump.

Mr Trump’s former lawyer Michael Cohen pleaded guilty this week to campaign finance violations alleging he, Mr Trump and the tabloid were involved in buying the silence of a porn actress and a Playboy model who alleged affairs.

Several people familiar with the Enquirer’s parent, American Media Inc., who spoke to the AP on condition of anonymity because they signed nondisclosure agreements, said the safe was a great source of power for Mr Pecker, the company’s CEO.

The Trump records were stored alongside similar documents pertaining to other celebrities’ catch-and-kill deals, in which exclusive rights to people’s stories were bought with no intention of publishing to keep them out of the news.

By keeping celebrities’ embarrassing secrets, the company was able to ingratiate itself with them and ask for favours in return.

But after The Wall Street Journal initially published the first details of Playboy model Karen McDougal’s catch-and-kill deal shortly before the 2016 election, those assets became a liability.

Fearful that the documents might be used against AMI, Mr Pecker and the company’s chief content officer, Australian journalist Dylan Howard, removed them from the safe in the weeks before Mr Trump’s inauguration, according to one person directly familiar with the events.

It was unclear whether the documents were destroyed or simply moved to a location known to fewer people.

AMI did not immediately respond to a request for comment.

Mr Pecker’s immunity deal was first reported Thursday by Vanity Fair and The Wall Street Journal, citing anonymous sources. Vanity Fair reported that Howard was also granted immunity.

Court papers in the Cohen case say Mr Pecker “offered to help deal with negative stories about (Trump’s) relationships with women by, among other things, assisting the campaign in identifying such stories so they could be purchased and their publication avoided.”

The Journal reported Mr Pecker shared with prosecutors details about payments that Mr Cohen says Mr Trump directed in the weeks and months before the election to buy the silence of McDougal and another woman alleging an affair, porn star Stormy Daniels.

Daniels was paid $US130,000. McDougal was paid $US150,000.

While Mr Trump denies the affairs, his account of his knowledge of the payments has shifted. In April, Mr Trump denied he knew anything about the Daniels payment.

He told Fox News in an interview aired Thursday that he knew about payments “later on.”

In July, Mr Cohen released an audiotape in which he and Mr Trump discussed plans to buy McDougal’s story from the Enquirer. Such a purchase was necessary, they suggested, to prevent Mr Trump from having to permanently rely on a tight relationship with the tabloid.

“You never know where that company — you never know what he’s gonna be -” Mr Cohen says.

“David gets hit by a truck,” Mr Trump says.

“Correct,” Mr Cohen replies. “So, I’m all over that.”

While Mr Pecker is co-operating with federal prosecutors now, AMI has previously declined to participate in Congressional inquiries.

Last March, in response to a letter from a group of House Democrats about the Daniels and McDougal payments, AMI General Counsel Cameron Stracher declined to provide any documents, writing that the company was “exempt” from US campaign finance laws because it is a news publisher, and it was “confident” it had complied with all tax laws.

He also rebuffed any suggestion that AMI had leverage over the president due to its catch-and-kill practices.

“AMI states unequivocally that any suggestion that it would seek to ‘extort’ the President of the United States through the exercise of its editorial discretion is outrageous, offensive, and wholly without merit,” Mr Stracher wrote in a letter obtained by The Associated Press.

Former Enquirer employees who spoke to the AP said that negative stories about Mr Trump were dead on arrival dating back more than a decade when he starred on NBC’s reality show The Apprentice.

Media outlets are now reporting that Mr Trump’s bookkeeper for his personal and business affairs for decades has also been granted immunity in the federal probe of Mr Cohen.

The Wall Street Journal and NBC News were first to report on anonymous sources that longtime Trump Organization finance chief Allen Weisselberg got immunity to talk to federal prosecutors in the investigation of the hush money Mr Cohen paid to the two women.

Though not named in the Cohen case, Mr Weisselberg is believed to be one of two Trump executives mentioned in the suit who reimbursed Mr Cohen and covered up the payments by saying they were legal expenses.

In 2010, at Mr Cohen’s urging, the National Enquirer began promoting a potential Trump presidential candidacy, referring readers to a pro-Trump website Mr Cohen helped create.

With Mr Cohen’s involvement, the publication began questioning President Barack Obama’s birthplace and American citizenship in print, an effort that Mr Trump promoted for several years, former staffers said.

The Enquirer endorsed Mr Trump for president in 2016, the first time it had ever officially backed a candidate.

In the news pages, Trump’s coverage was so favourable that the New Yorker magazine said the Enquirer embraced him “with sycophantic fervour.”

Positive headlines for Mr Trump, a Republican, were matched by negative stories about his opponents, including Hillary Clinton, a Democrat: An Enquirer front page from 2015 said Hillary: 6 Months to Live and accompanied the headline with a picture of an unsmiling Clinton with bags under her eyes.