Newsweek, once one of the most powerful publications in US media, has a scoop on its hands – one that has plunged the troubled title further into chaos.

On Tuesday the magazine published an exposé of its owner’s ties to a small evangelical Christian school, Olivet University, founded by the controversial Korean pastor David Jang.

Staff were fired and several editors threatened to resign as management tried to interfere in the publication of the story.

The story – entitled “Why is the Manhattan DA looking at Newsweek’s ties to a Christian university?” – details links between Newsweek Media Group and Olivet University’s efforts to develop a campus in upstate New York.

The Manhattan district attorney’s office raided the downtown newsroom of Newsweek in January, taking 18 computer servers. Its investigations have been reported to be into ties between Olivet and Newsweek Media Group, formerly known as IBT Media.

Jonathan Davis, co-founder of Newsweek Media Group, is the husband of Tracy Davis, president of Olivet University.

After the raid Olivet denied “shared ownership interests” with Newsweek but acknowledged “payment for a licensing and R&D arrangement”.

According to the Newsweek report, tax records show Newsweek Media Group paid Olivet millions of dollars for licensing and research and development agreements. Olivet also offered New York county officials free advertising in Newsweek, according to the report, as it sought permits and tax breaks for its new campus. In 2017 Newsweek ran 10 full-page ads – valued at about $149,000 (£106,000) – promoting local services, all free of charge.

“At the same time as Newsweek Media Group was giving away $150k in free advertising as part of negotiations to secure property for Olivet University, I watched reporters in tears as they laid off two-thirds of the people in the newsroom,” Newsweek’s associate politics editor, Jason Le Miere, tweeted on Tuesday night

The story was accompanied by an extraordinary editors’ note describing turmoil at the magazine and “egregious breaches of confidentiality and journalism ethics”.

“As we were reporting this story, Newsweek Media Group fired Newsweek editor Bob Roe, executive editor Ken Li and senior politics reporter Celeste Katz for doing their jobs,” it read.

“As we continued working on the story, we were asked to take part in a review process which, we ultimately learned, involved egregious breaches of confidentiality and journalism ethics.”

The editors claimed “subjects of the story were shown parts of the draft, if not the entire piece, prior to publication by a company executive who should not have been involved in the process”.

The Daily Beast, which used to be owned by the same company as Newsweek, reported that the story had been in the works for weeks and had encountered “significant headwinds” from management.

The editors and reporters involved in the Olivet piece said they resisted efforts of management to influence the story and “felt they would be forced to resign”.

However, a senior Newsweek Media Group executive then promised that the company’s owners would ensure editorial independence in the future.

Eventually the story was published, but not without another note at the bottom reading: “Celeste Katz contributed reporting to this article before she was fired.”

Newsweek Media Group, which bought the 85-year-old publication in 2013, did not immediately return a request for comment.