The search for 34-year-old Nathan Dale Blankenship started Tuesday afternoon, when authorities alerted the Marshall County Sheriff's Office that the missing Oklahoma City man might be in Texoma, and foul play might be involved.
"We aren't sure if Mr. Blankenship left on his own volition or if he is the victim of a crime," said OSBI public information officer Jessica Brown.
Marshall county Sheriff Ed Kent said Blankenship was last seen Saturday morning in Oklahoma City with Jessica Cornwell.
Authorities said they want to speak with her, but haven't found her yet.
Blankenship is 5' 9" and weighs 250 pounds. He has black hair and brown eyes.
The search for him started in Oklahoma City, but a tip led investigators south to Marshall County.
"The reporting parties suggested that they had left Oklahoma City in the wee hours of Saturday morning and were en route to Madill," said Sheriff Ed Kent.
Kent also said since then, he and his deputies have searched the county--specifically the Cumberland Bottoms area-- for any sign of Blankenship.
They're also receiving help from the Bryan county and Johnston county sheriff's offices.
He says the search could take days.
"Until we have no further leads or no further area to cover," he said. "It's a pretty big area."
UPDATE 2/8/13-- Authorities are expanding their search in Marshall County for a missing Oklahoma City man.
The sheriff's office got a tip yesterday that Nathan Dale Blankenship might be in the area. This afternoon they began searching an area 30 miles north of Cumberland Bottoms, where they searched yesterday.
The Bryan county sheriff's office also searched their side of the Washita River yesterday.
So far there's still no trace of Blankenship, and the OSBI said it's the lack of information that makes this case suspicious.
"Since we don't know where he is, what condition he's in or if foul play has occurred that's why we're looking at it as a suspicious disappearance," said OSBI public information officer Jessica Brown.
Blankenship has been missing since Monday.