STOCKTON  (AP) — The sheriff of San Joaquin County plans to ask the FBI to take over the job of searching for and recovering the remains of victims linked to two serial murderers known as the Speed Freak Killers following criticism of his agency's handling of the delicate retrieval operation.

Sheriff Steve Moore announced his intentions Tuesday after the mother of one of the victims and a local congresswoman said they think federal investigators are better equipped for a task that involves multiple sets of remains and multiple sites.

Joan Shelley said remains of her 16-year-old daughter, JoAnn Hobson, were returned to her mixed with bones from at least three other people who were discovered in a Linden well. A forensic anthropologist at California State University, Chico, determined that the large earthmoving equipment the sheriff's department used was a factor in the comingling of the remains, Shelley said.

"I don't want the rest of the families to go through this," she said.

The FBI has been working with the Sheriff's Department since March to search the well and to make excavation plans for four other sites where death row inmate Wesley Shermantine said he and his late co-conspirator, Loren Herzog, disposed of as many as a dozen victims from their killing spree in the 1980s and 90s.

"If they want to come in to take it over, that's fine with me," Moore said. "If they want to assume all the costs, that's also fine with me."

The San Joaquin County Board of Supervisors on Tuesday approved the sheriff's request for $126,000 to continue work at the Linden well and asked him to find out within two weeks if the FBI is willing to assume responsibility for the case.