In a Monday morning massacre, Newsweek fired Editor-in-Chief Bob Roe, Executive Editor Ken Li and investigative reporter Celeste Katz, The Post has learned.

All three were working on a story about the news site’s parent company and its possible financial ties to Olivet University, a fundamentalist Christian college founded by the controversial Korean-American pastor Rev. David Jang.

Hours after the shocking dismissals, the parent company, Newsweek Media Group, appointed Nancy Cooper, the managing editor of sister title International Business Times, as acting editor of Newsweek.

In the Cooper announcement, NMG did not mention the firings — noting only that Roe and Li would be leaving the publication “immediately.”

Newsweek has been in a gathering cloud of controversy, especially since Jan. 18, when dozens of investigators from the Manhattan District Attorney’s office raided the site’s Lower Manhattan offices — and left hours later with 18 computer servers.

The DA, in the midst of a 18-month probe of NMG, is said to be focusing on its financial ties to Olivet.

In a bizarre twist, NMG co-founder Jonathan Davis — who was fingered in a Newsweek report for having an $800,000 federal tax lien filed against him last October — will return to the company as interim chief content officer, the company said Monday.

Davis and co-founder Etienne Uzac, the former chief executive, had been removed from day-to-day involvement with NMG in mid-2016 as the company ran into serious cash problems. NMG laid off more than 40 staffers and flew in Dev Pragad from the international operation to take over as chief executive. Uzac remained as chairman until last week when he resigned along with his wife, NMG finance director Marion Kim.

The most recent chief content officer, Dayan Candappa, was suspended last week after BuzzFeed reported he had been fired from a previous job, at Reuters, for pressuring a young female reporter to have sex with him. NMG last week hired an outside law firm to investigate the allegations.

Two other senior Newsweek reporters — Josh Saul and Josh Keefe, who were also working on the investigation into possible NMG-Olivet financial ties — were rumored to be on the hot seat. They couldn’t be reached for comment but sources late Monday said they remain employed at NMG, previously known as IBT Media.

Olivet, in an expansion move, in 2014 bought a vast tract of land in Wingdale, NY, in leafy Dutchess County, roughly 75 miles north of Midtown Manhattan, that previously housed the Harlem Valley Psychiatric Center.

The gloomy site had been closed by the state since 1994 and its crumbling buildings remain vacant to this day.

Keefe was recently in Wingdale talking to neighbors of the sprawling property, sources said.

Adding to Newsweek’s woes, BuzzFeed News reported that IBT fraudulently inflated its ad traffic figures in order to snag a lucrative contract from the federal Consumer Financial Protection Bureau. NMG denied the fraud allegations but conceded that it did purchase a “very small percentage” of its traffic.

Olivet had previously denied it had financial links to NMG.