The investigation into Nancy Guthrie's case just took a major forensic turn ... TMZ has confirmed.

An FBI spokesperson tells TMZ ... a glove recovered in the case contains a DNA profile that appears to match the gloves worn by the unidentified subject captured on the security camera footage released from Nancy's front door cameras.

According to the feds, investigators collected roughly 16 gloves scattered around areas near the house. But authorities say most of those belonged to volunteer searchers who tossed them aside while combing the neighborhood.

"The one with the DNA profile recovered is different and appears to match the gloves of the subject in the surveillance video," the FBI's statement said. The glove in question was discovered in a field along the side of a road about two miles from Nancy's multimillion-dollar home.

The FBI says it received preliminary results Saturday and is now waiting for quality control and official confirmation before entering the unknown male's DNA profile in the FBI's national DNA database, which takes about 24 hours.

As you know ... Savannah Guthrie's mom was reported missing February 1. The FBI later released footage from a doorbell camera, showing the alleged kidnapper lurking around the front door of Nancy's house.

The prowler was wearing a mask and gloves with a holstered gun around his waist.