- Israel Keyes is believed to have killed 11 people before his death in December, the FBI says
- He admitted to eight slayings after his arrest in March 2012
- The FBI is asking for the public to help them identify other victims
(CNN) -- Federal agents say they've now linked 11 killings to admitted serial killer Israel Keyes and are looking into possible ties to killings in other countries.
Keyes killed himself in December, about nine months after his arrest in the slaying of an Anchorage, Alaska, coffee barista. Police said he admitted to at least seven other slayings, from Vermont to Washington state, before his death.
In a statement issued Monday afternoon, the FBI office in Anchorage said agents have now added three more to that grim tally, based on his statements:
-- a pale-skinned woman in an older car, "possibly having a wealthy grandmother"
A lab has matched DNA recovered from the body of Mary Sullivan with that of her suspected killer -- the confessed Boston Strangler Albert DeSalvo. After a sample was secretly collected from a relative, DeSalvo's body was exhumed for more DNA testing. DeSalvo was stabbed to death in 1973 while serving a prison sentence for rape. Click through to see more of history's infamous killers. 
Ed Gein killed at least two women and dug up the corpses of several others from a local cemetery, using their skin and body parts to make clothing and household objects in Wisconsin in the 1950s. 
In 1973, Juan Corona, a California farm laborer, was convicted and sentenced to serve 25 consecutive life sentences for the murder of 25 people found hacked to death in shallow graves. 
In 1977, David Berkowitz, also known as Son of Sam, confessed to the murders of six people in New York City. Berkowitz, now serving six consecutive 25-to-life sentences, claimed a demon spoke to him through a neighbor's dog. 
Cousins Kenneth Bianchi, seen here, and Angelo Buono were charged with the murders of nine women between 1977 and 1978. Also known as the Hillside Stranglers, the cousins sexually assaulted and sometimes tortured their victims, leaving their bodies on roadsides in the hills of southern California. 
Wayne Williams killed at least two men between 1979 and 1981 and police believed he might have been responsible for more than 20 other deaths in the Atlanta area. Williams was convicted and sentenced to two life terms in 1982. 
After serving 15 years for murdering his mother, Henry Lee Lucas was again convicted in 1985 for nine murders. Lucas was the only inmate ever spared from execution by then-Texas Gov. George W. Bush. 
Richard Ramirez, also known as the Night Stalker, was convicted of 13 murders and sentenced to death in California in 1989. The self-proclaimed devil worshiper found his victims in quiet neighborhoods and entered their homes through unlocked windows and doors. 
During a routine traffic stop, a policeman found a dead Marine in the front seat of a car driven by Randy Steven Kraft. Kraft picked up hitchhikers, gave them drugs and alcohol, sexually assaulted them, then mutilated and strangled them. He was linked to 45 murders and sentenced to death in 1989. 
Ted Bundy raped and killed at least 16 young women in the early to mid-1970s before he was executed in 1989. A crowd of several hundred gathered outside the prison where he was executed, and they cheered at the news of his death. 
Jeffery Dahmer was sentenced to 15 consecutive life terms for the murders of 17 men and boys between 1978 and 1991 in the Milwaukee area. Dahmer had sex with the corpses of his victims, kept bodies parts of others and ate the body parts of some. Dahmer and another prison inmate were beaten to death during a work detail in November 1994. 
John Wayne Gacy killed 33 men and boys between 1972 and 1978. Many of his victims, mostly drifters or runaways, were buried in a crawl space beneath his suburban Chicago home. 
Joel David Rifkin was stopped by police for driving without a license plate when a body was found in his pickup truck. Rifkin killed 17 women in New York City between 1991 and 1993 and was sentenced to life in prison. 
Charles Ng, seen here, and accomplice Leonard Lake tortured, killed and buried 11 people in northern California between 1984 and 1985. After the men were arrested for shoplifting, police found bullets and a silencer in their car and took them into the police station for questioning, where Lake killed himself with a cyanide pill. Ng was later sentenced to death. 
Robert Lee Yates Jr. killed 15 people, most of them between 1996 and 1998. He buried one of them in a flowerbed by his house in the Spokane, Washington, area. Most of his victims were prostitutes or drug addicts he killed in his van. He is on Washington's death row. 
Gary Leon Ridgway, also known as the Green River Killer, confessed to 48 killings after his DNA was linked to a few of his victims. Remains of his victims, mostly runaways and prostitutes, turned up in ravines, rivers, airports and freeways in the Pacific Northwest. 
Aileen Wuornos was executed in Florida in 2002 for the murders of seven men whom she had lured by posing as a prostitute or a distressed traveler. 
Derrick Todd Lee was accused of raping and killing six women in Baton Rouge, Louisiana, between 2001 and 2003. He was arrested in Atlanta for the murder of Charlotte Murray Pace convicted in 2004 and sentenced to death. 
Danny Rolling pleaded guilty to the 1990 murders of five students in Gainesville, Florida, whom he raped, tortured and mutilated. Rolling was also responsible for a separate 1991 triple homicide in Shreveport, Louisiana, and executed in 2006. 
Angel Maturino Resendez, also known as the Railway Killer, was a drifter from Mexico. During the 1990s he robbed and killed his victims near railroad tracks on both sides of the border, then would hop rail cars to escape. Resendez was in U.S. Border Patrol custody but was let go and killed four more people before being arrested, tried and convicted in Texas. He was put to death in 2006. 
Pig farmer Robert Pickton was charged with 26 counts of murder after police found the bodies of young women on his farm in Port Coquitman, British Columbia. He was convicted of six murders in 2007 and is serving a life sentence. 
The BTK Strangler, Dennis Rader, killed 10 people between 1977 and 1991 in the Wichita, Kansas, area. He was convicted to 10 consecutive life terms in 2005. Rader named himself BTK, short for "bind, torture, kill." 
Police found the decomposing and buried bodies of 10 women, and the skull of another, at the Cleveland, Ohio, home of ex-Marine Anthony Sowell. Sowell was convicted and given the death penalty in 2011. 
Chester Dewayne Turner was charged with murdering 10 women and one unborn fetus in the Los Angeles area between 1987 and 1998. In 2007, Turner was sentenced to death for the murders and charged with four more murders in 2011. 
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Photos: Infamous serial killers -- one in which the victim was posed to make it look like the death had been an accident
-- one "in Texas or a surrounding state" that he had denied committing before his death.
Travels abroad
They also asked the public to share any information they had regarding Keyes' travels in Canada, Mexico and Belize between 2001 and 2008.
"Keyes traveled internationally and it is unknown if he committed any homicides while outside of the United States," the FBI statement said.
Keyes lived in upstate New York at one point and "reported several trips to Montreal in which he sought out prostitutes" and drove through western Canada on his way to Alaska, where he lived before his arrest.
'A murder addict'
An Anchorage police officer described Keyes as a kind of murder addict who hunted victims in remote locations like parks, campgrounds or hiking trails.
An Army veteran and contractor, Keyes studied other serial killers but "was very careful to say he had not patterned himself after any other serial killer," Detective Monique Doll said in December.
No remorse
Keyes killed himself by slitting one of his wrists and strangling himself with bedding, police said. He left behind an extensive, four-page note that expressed no remorse nor offer any clues to other slayings.
Investigators said he had "a meticulous and organized approach to his crimes," stashing weapons, cash and items used to dispose of bodies in several locations to prepare for future crimes.
Authorities have dug up two of those caches -- one in Eagle River, Alaska, outside Anchorage, and one near a reservoir in the Adirondack Mountains of New York.
Keyes also said he robbed banks to finance his travels, and investigators have corroborated his role in two holdups, the FBI said.
