Nancy Guthrie Investigation Faced Costly Early Blunders, Report Says

The search for Nancy Guthrie may have been botched from the very beginning ... with a new report detailing a string of costly blunders in the crucial hours after she vanished.

According to The Wall Street Journal, Pima County Sheriff's deputies initially gave little attention to dried blood on Nancy's front porch -- reportedly wondering whether it came from an unrelated head bump or nosebleed. Testing later confirmed it was Nancy's blood ... and authorities now believe it was connected to her kidnapping.

The outlet reports deputies also failed to immediately tape off the Tucson property ... leaving reporters, livestreamers, and even Amazon and pizza delivery drivers free to approach the porch. Authorities didn't put up crime-scene tape until three days after Nancy disappeared.

Meanwhile, investigators reportedly burned precious time debating whether they had a kidnapping or a routine missing-person case on their hands.

The department's $1.7 Million surveillance plane also remained grounded for hours ... because it couldn't find a deputy qualified to operate the aircraft's camera system, according to the report. The plane allegedly didn't begin searching until around 6:30 PM ... when darkness limited what its zoom camera could capture.

Sheriff Chris Nanos disputed WSJ's findings and insisted the case remains active. The FBI told the outlet Pima County has always led the investigation and said some requests for federal assistance came late.

As TMZ has reported, Nancy disappeared from her Tucson home overnight on February 1 -- authorities believe she was abducted -- and she remains missing. Authorities recently released two notes sent after the abduction -- one demanding millions in Bitcoin and another claiming Nancy died "shortly" after she was taken and was "buried in nature."