YAKIMA, Wash. — An FBI probe into more than a dozen unsolved deaths on the Yakama reservation won’t yield any new charges, but federal authorities have confirmed they were not the work of a serial killer.

Federal officials on Wednesday released the results of a more than two-year investigation of the deaths of 16 woman dating back to the early 1980s as a cold-case initiative promised by former U.S. Attorney General Alberto Gonzales.

Although the probe didn’t turn up enough evidence to move forward with any charges, it did shed some light on the nature of many of the cases, said U.S. Attorney Jim McDevitt in Spokane.

“I think what the probe did, I would hope for the last and final time, was dispel any notion that this was the work of a serial killer — it’s not,” he said Wednesday by telephone. “I think this was the most extensive, comprehensive review to date that has garnered every shred of evidence that law enforcement had.”

The probe mainly focused on a string of deaths from 1980 to 1993. Shari Dee Sampson Elwell, whose strangled and sexually mutilated body was found in a remote area of the 1.2 million-acre Yakama reservation, was the last victim during that period.

In many of the cases, evidence was eroded by exposure and the elements. In others, only skeletal remains were found. The deaths stymied investigators for years and instilled fear in an otherwise close-knit American Indian community. Some suspected a serial killer was at work.

In three cases, “significant evidence” was developed about the identity of suspected perpetrators, the FBI said. But there wasn’t enough physical evidence and witness statements to warrant charges.

Some of the cases may never be solved, McDevitt said.

“Unfortunately, that’s always a possibility,” he said. “You’d like to say that you could solve every crime.

“This isn’t the end of it. I think it’s the end of the chapter of whether there is a serial killer loose.”

The report was to be released in January but was delayed because of the investigation into the death of Daisey Mae Tallman, whose skeletal remains were believed to be found in May 2008. Investigators are waiting for DNA test results to confirm the victim’s identity.

Of the 16 cases, two resulted in convictions for murder. Ten are believed to be homicides, two were ruled accidental drownings, one was hypothermia and another was inconclusive, according to the FBI news release.

Back in the 1980s, when the cases were being actively investigated, at least two investigators from Yakama tribal police and the Bureau of Indian Affairs said they saw similarities in the victims, such as the women’s ages and race. Most of the women who were killed were Native American.

In 2001, prosecutors used DNA evidence to convict John Bill Fletcher for the 1987 stabbing deaths of Theresa Branscomb and Bertha Cantu. Samuel Posada was charged in January of this year with the 1987 rape and strangulation of a third victim, 20-year-old Jenece Marie Wilson.

At one point, a spokesman with the FBI has said there may be as many as 32 unsolved cases on the Yakama reservation involving missing persons and deaths.

The cases were reopened after then-Attorney General Gonzales visited the Yakama reservation in March 2006 and promised a cold-case initiative in response to the staggeringly high number of unsolved deaths throughout Indian Country. The first federal probe began with the Yakamas.

The FBI has jurisdiction to investigate all serious crimes involving Native Americans on tribal lands.

Local families of the victims remain skeptical whether authorities put enough effort and resources into solving the cases.

Many complained that FBI agents didn’t show up years ago to conduct any field investigations.

Caroline Looney said she still hasn’t been interviewed by an FBI agent in the death of her 39-year-old sister, Alice Ida Looney. She went missing in August 2005, and her body was found wedged under a tree in Satus Creek southeast of Toppenish on Nov. 30 of that year.

The FBI lists the cause of her death as inconclusive.

“We’ve been sitting here waiting, just like all these other families,” Caroline Looney said by telephone Wednesday. “This sounds like they’re really not going to do anything in her case. I just wish they could have contacted us.”

The FBI said they remain committed to investigating new leads involving the cold cases.

Federal officials said they plan to invite the Yakama Nation to form a task force within the next 18 months to fight illegal drug trafficking and violent crime in Indian Country. Officials pointed to the Salish Safe Trails Task Force, which includes the FBI and serves the Colville, Spokane and Kalispel reservations in Eastern Washington.

With the task force, the FBI said, would come funding for vehicles, office space, specialized equipment, training, overtime money and federal deputation of task force officers.