TUCSON, Ariz. (AP) — A registered sex offender jailed since last year has been charged in the kidnapping and killing of two Arizona girls who went missing in 2012 and 2014, authorities announced Saturday.

Christopher Matthew Clements, 36, was indicted on Friday by a grand jury on 21 criminal counts, including murder and kidnapping charges in the deaths of 6-year-old Isabel Celis and 13-year-old Maribel Gonzalez, Tucson Police Chief Chris Magnus said.

Celis went missing from her Tucson home in April 2012, and her body was discovered in what was described as a rural area in March 2017.

Gonzalez’ body was discovered in June 2014 in the Avra Valley community near Tucson, not far from where Celis’ remains would be found three years later.

Magnus and other officials held a news conference to announce the indictment. But they declined to answer questions from reporters and did not disclose how the girls died or what prompted authorities to investigate Clements in the killings, except to say that the FBI in 2017 learned Clements might have information about the death of Celis.

He then provided information to authorities that led to the discovery of Celis’ remains, Magnus said. Investigators later discovered additional pieces of evidence, but they did not describe Saturday what they had found.

Clements had already been in a Phoenix-area jail for more than a year facing other charges when the indictment was issued.

Pima County Attorney Barbara LaWall called the identification of Clements as the killer of the girls “long overdue.”

“The heart-wrenching tragedies of Maribel Gonzalez and Isabel Celis’ murders have been compounded by a very long, long wait for justice,” she said.

Celis’ father reported the girl missing on the morning of April 21, 2012, after he went to her bedroom and she was not there.

Police previously did not name suspects, but they said they found “suspicious circumstances around a possible entry point” into the home.

A medical examiner last year ruled Isabel Celis’ death as “homicide by unspecified means.” A heavily redacted autopsy report did not indicate how she died.

Gonzalez went missing on her way to a friend’s house. Her body was found days later.

Clements made his first court appearance Saturday morning. He does not yet have an attorney but will be assigned one at a Sept. 24 arraignment.

Clements was being held on a $2 million bond, Tucson Police Sgt. Pete Dugan said.

Clements was jailed in April 2017 on suspicion of burglary, theft and fraudulent schemes, Maricopa County Sheriff’s Sgt. Bryant Vanegas said Saturday. Vanegas did not have information about when Clements might be transferred to southern Arizona to face charges in the case of the girl’s killings.

The indictment made public Saturday did not provide any details about how the girls were killed or what evidence linked Clements to the killings. It said he was also charged with burglary, theft and possession or distribution of child pornography in other cases dating from 2012 through 2016.

Clements was charged and convicted in Oregon in 1998 of sex-related crimes and was required to register as a sex offender. He was charged and convicted in 2006 in Bay City, Florida, for failing to register, according to Florida law enforcement records.

He was also charged in 2008 in Tucson with failing to register as a sex offender. He was convicted and sentenced to serve 46 months in prison and five years of supervised release

The Ninth Circuit Court of Appeals reversed that sentence in 2011, finding that the federal law requiring him to register as a sex offender within three days of moving to a new home was passed after his 1998 conviction and therefore did not apply to his crime.