LINDEN (CBS13) – A letter from death row claims FBI investigators who are searching for more “Speed Freak Killer” victims are digging in the wrong spot.

In the latest letter from death row, convicted killer Wesley Shermantine claims FBI agents are off by 200 yards.

“They went out there and dug 200 feet into the earth at some place they picked out, I never sent them there,” Shermantine’s letter read.

State Senator Cathleen Galgiani received the letter along with a copy of one addressed to an FBI agent on Wednesday.

“I’m very concerned that if they are in the wrong place, not where Wesley has directed them to, and if they don’t find remains, they will shut it down and say his information is not accurate when in fact they are not where he directed them to,” said Galgiani.

FBI crews have spent almost two weeks preparing the well for Thursday’s excavation. Previous maps and tips from Shermantine led local investigators to a previous well that yielded the remains of JoAnn Hobson, Kimberly Billy, an unidentified woman and a fetus.

The remains of Cyndi Vanderheiden and Chevy Wheeler were discovered in Calaveras County.

Galgiani hopes investigators take Shermantine’s claims seriously.

“My hope now is that they go back and interview Wesley Shermantine and talk to him more about the locations he directed him to,” Galgiani said.

The FBI says agents are the ones deciding where to dig.

“Convicted serial killer Wesley Shermantine’s recollections have occasionally proved to be inaccurate and only with thorough investigation and careful consideration of all information available have we been able to locate a site that offers the best chance of recovering victim remains,” an FBI statement read.

The FBI is expected to reveal its findings once the dig wraps up, which could be days, if not weeks.