(WXIA) -- The FBI is offering a reward of up to $20,000 for any information about a missing Putnam County woman.
Just after noon Tuesday, Georgia Department of Natural Resources rangers launched a specially equipped pontoon boat brought in from Lake Lanier to search a portion of Lake Oconee for 87-year-old Shirley Dermond.
She's been missing for exactly one week since the decapitated body of her husband, Russell, 88, was found in the garage of their nearby lakefront home.
In addition to side image sonar, the DNR team also has an underwater robot submersible with a color video camera and lights. It's capable of searching as far 300 feet from the boat and can give clear pictures of the bottom.
Unlike Lake Lanier, which is nearly 200 feet deep, most of the search area on Lake Oconee is only 20 to 30 feet deep.
DNR ranger Richard Tanner told 11Alive the team will search until after dark Tuesday and for the rest of the week, if necessary, to see if the missing woman's body might be in the lake.
He said while the work can be emotionally draining, his team's goal is to bring closure to the family.
The DNR team has already used just the sonar to search the lake shoreline about five miles around the Dermond home.
Meanwhile, Putnam County Sheriff Howard Sills, whose department is investigating the case, is not commenting on what, if any, leads he has in the mysterious case.