Both girls were found dead near Trico and West Avra Valley roads outside of Tucson.
According to the documents, the investigation began in February 2017 when Clements' then fiance, called the FBI and said Clements knew where Isabel was buried.
In a letter to his fiance, Clements claimed there was a total of four bodies buried in that desert area outside of Tucson. Authorities believe two of the four are Isabel and Maribel. They do not know who the other two are.
Isabel was 6 years old when she vanished from her parents' east-side home in April 2012. Maribel was 13 years old when she went disappeared while walking to a friend’s house in 2014.
Maribel's body was found a few days after she went missing. Isabel's remains were not located until March 2017.
BREAK IN THE CASE
The FBI interviewed Clements in February 2017 and he said he knew where Isabel was buried but refused to lead them to her unless two Pima County burglary cases against him were dismissed. Authorities also agreed to release Clements' vehicle, which was being held in the burglary case.
On March 3, Clements led agents to the area of Trico and West Avra Valley roads.
Isabel's remains were found soon after.
During the search, Clements pointed out an area that had numerous discarded tires. He told them it was a landmark he remembered.
The tire area is where authorities had found Maribel’s body in 2014. According to the court documents, a DNA test put Clements near Maribel’s body.
Clements told investigators he did not kidnap or kill Isabel but he refused to say how he knew where she was buried.
Clement is being held in the Maricopa County Jail on burglary charges unrelated to anything in Pima County.
He told agents he knows what weapon was used to kill Isabel, but refused to tell authorities where it was unless the Maricopa County burglary charges are dropped and he is allowed to go home.
After the discovery, investigators found out Clements was a registered sex offender who lived in Oregon, Washington, Florida and Arizona.
In 1998, he was convicted of attempted unlawful sexual penetration with a foreign object in Oregon.
In 2006, Clements was convicted of failure to register as a sex offender while living in Florida.
When he was 11, he was accused of molesting a very young child but he was never charged.
At one time, Clements and his fiance lived at a home on East Elida Street in Tucson.
During the investigation, authorities found a plastic container buried in the backyard.
In the container, they found a young child's sweatshirt and homework with the name "Mercedez" on it. Mercedes was Isabel's middle name.
Investigators said they found what appeared to be ashes on the ground.
Before that, Maricopa County authorities seized several items from the East Elida home, including computers and media storage devices.
Child porn and sexually explicit photos involving children were found in a search of the computers and drives.
The computers also turned up interesting search histories, according to investigators.
Some of the search terms include:
- Isabel Celis sexy
- Child killer found not guilty
- Body found in desert
- Arizona cold cases
- Kauilani Tadeo
- Dana Ireland autopsy photos
Kauilani Tadeo is a 6-year-old girl Hawaiian girl who was raped and killed in 2001. Mark Davis, the man accused of killing Kauilani, was found dead in his cell in 2013.
Dana Ireland was hit by a vehicle while riding her bike in Hawaii in 1991. She was kidnapped and raped before dying from her injuries.
When investigators searched Clements' jail cell in Maricopa County, they found the name of an inmate in Pima County.
The inmate identified Clements from a photograph and told authorities Clements started talking to him about the Celis case.
Clements allegedly told the other inmate that there was "damning evidence" in the trunk of Clements car and he "had to get it back."
The unnamed inmate said Clements told him "Isabel was strangled and chemicals were poured over her body."
Clements also allegedly said that Isabel was never supposed to survive the kidnapping.
The inmate said Clements showed him photos he had hidden in his Bible, photos that were allegedly of the Celis home.