The FDR bible used by Mayor Bill de Blasio for his swearing in vanished after the New Year’s Day ceremony, sparking a panicked, hours-long search for the historic tome.

“They had the whole detail looking through blankets,’’ a police source said of the scramble by at least 50 NYPD detectives and city officials to find the Bible, which was given to President Franklin Delano Roosevelt as a gift at his first inauguration in March 1933.

Former President Bill Clinton performed the ceremony Wednesday as de Blasio laid his hand on the bible.

But around 2:30 pm, the bible was nowhere to be found, a source said, sparking a massive book-hunt at City Hall.

“We were looking in garbage cans outside, in all the bags,” one searcher said.

“It’s the FDR Bible!” said another.

When it was found, just before 5 pm, one of the detectives held it aloft at the top of the stairs in the rotunda, shouting, “We found it!’’ as a crowd broke out in applause.

A de Blasio spokesman declined to comment.

The historic bible — with “The White House” embossed on the front — is one of several in a collection held at the FDR Presidential Library in upstate Hyde Park.

Library director Lynn Bassanese, who loaned the tome to de Blasio, told the Poughkeepsie Journal that FDR signed the Bible.

“Since FDR signed it and dated it for his very first inauguration, we thought that was particularly symbolic for the mayor-elect,” she said.

A member of the New York Public Library contacted the folks at the FDR library about borrowing a Bible, she said.

Bassanese has said she planned to personally bring the book to the swearing-in, and vowed to “wait there for the ceremony to be done and then I will carry it back.’’

She did not immediately return a call for comment.