SACRAMENTO -- The FBI is preparing to excavate an old, closed well on private property in San Joaquin County to search for the remains of two serial killers' victims from the 1980s and '90s, officials said Monday.

The FBI took over responsibility for the excavation from the San Joaquin County Sheriff's Department, which was criticized for its handling of the operation.¿

The well, located in the small town of Linden, has been linked to Wesley Shermantine and Loren Herzog, the so-called "Speed Freak Killers," who authorities say went on a methamphetamine-fueled killing spree in the 1980s and '90s.

The new excavation effort, to last two weeks, is the result of several months of multi-agency investigative collaboration. The site is deemed the most likely to yield remains of victims still undiscovered, FBI officials said Monday at a press conference in Sacramento.

"We all remain hopeful that our efforts at this site will ultimately return the remains of victims to their loved ones, but know that such is not a certainty," Herbert H. Brown, special agent in charge of the Sacramento Division of the FBI, said Monday. "Our hearts go out to the many families who hope that this excavation may bring closure to their long, painful wait for the return of their loved ones. We will not recklessly speculate; our goal is to offer incontrovertible fact to our law enforcement partners, the families of the missing and the public."

Whose remains, if any, may be found at the new location is unknown, authorities said.

San Joaquin County Sheriff's Office investigators and FBI personnel remain "cautiously optimistic" about the potential for recovery at the well site that may bring closure to one or more families of the missing. If remains are found during the excavation process, all will be sent to the FBI laboratory in Quantico, Va., authorities said.

Statements about any remains found will be held until laboratory results can confirm the identity of the individual or individuals recovered, authorities said.

The team working at the well site includes local and national FBI; investigative resources from San Joaquin County; forensic anthropologists from Chico State University; and contractors with specific technical experience required for excavation of the site.

The excavation is estimated to take approximately two weeks. Initial site preparation was under way Monday morning and heavy equipment will remove soil for the initial dig process. Once the soil is cleared, the team will begin excavating the site largely by hand, authorities said.

Abandoned wells in the area are known to be dumping sites for refuse including car parts and appliances.

Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.