In the wake of last week’s revelation of new DNA evidence in the unsolved slayings of Shirley and Russell Dermond at Georgia’s Lake Oconee, the reward has increased for information that leads to an arrest in the decade-old case.

Putnam County Sheriff Howard Sills on Monday said that late last week the FBI informed him the agency would be adding $20,000 to the case’s reward fund. Combined with the FBI’s offering, that fund now totals about $25,000.

The sheriff hopes the reward, which could possibly double if other donors come through, will spur tipsters.

“Here’s $25,000,” Sills said, addressing potential informants. “And there’s a possibility there’s another $30,000. And if you want to collect this, now’s the time to give us a call. Because if our DNA research pans out, we won’t need your call.”

The DNA that Sills referred to involved traces of cellular evidence detected on a clothing item that Russell Dermond, 88, had on at the time of his death.

On the morning of May 6, 2014, his decapitated body was found on the floor of his two-car garage in the Great Waters subdivision. It’s believed the killing took place a couple of days prior. The body of his wife, Shirley Dermond, 87, turned up May 16, 2014. It had been weighed down with concrete blocks and dumped in the water 5 miles down the lake.

The macabre, puzzling nature of the case has generated widespread interest and attracted the attention of numerous true-crime TV shows and podcasts. It has also prompted a number of tipsters to phone in what they think are useful hints or possibilities. So far none has proved helpful.

“The problem with this case,” Sills recently told The Atlanta Journal-Constitution, “is there’s no theory so far that fits it.”

Reward offerings in the case have fluctuated over the years. With this week marking the 10th anniversary of the killings, officials expect news coverage of the crimes to generate a fresh round of potential tips.