A parade of sheriff's and FBI vehicles, including forensics vehicles, passed through the roadblock on Friday that was set up about 3km from the house in Arizona.
The Pima County Sheriff's Department said the activity was part of the Guthrie case.
But it said further information was unavailable since it was a joint investigation with the FBI.
Guthrie, 84, was reported missing on February 1.
Authorities say her blood was found on the front porch of her Tucson-area home.
Purported ransom notes were sent to news outlets, but two deadlines for paying have passed.
Authorities have expressed concerns Guthrie's health because she needs daily medication.
She is said to have a pacemaker and has dealt with high blood pressure and heart issues.
Investigators have studied surveillance video, sorted through thousands of tips and submitted DNA and other evidence for laboratory analysis.
The FBI said it has collected more than 13,000 tips since the day Guthrie was reported missing.
The sheriff's department said it had taken at least 18,000 calls.
On Tuesday, authorities released footage showing an armed, masked person at Guthrie's doorstep on the night she was abducted.
The videos - less than a combined minute in length - gave investigators and the public their first glimpse of who was outside Guthrie's home in the foothills outside Tucson.
Experts say the video could contain a mountain of clues.
25°C