New Hampshire authorities announced that the case of missing child Harmony Montgomery is now a homicide investigation. 

"Harmony Montgomery was murdered in Manchester, New Hampshire, in the beginning of December 2019," New Hampshire Attorney General John Formella said Thursday, citing evidence officials have collected. 

Montgomery went missing at age 5 sometime between Nov. 28 and Dec. 10, 2019, but police only learned of her disappearance two years later. Her remains have not been found. 

"I'm beyond saddened that we stand here today to announce that the disappearance of Harmony Montgomery is now officially a homicide investigation," Manchester Police Chief Allen Aldenberg said Thursday at the press briefing. 

HARMONY MONTGOMERY: EXTENDED FAMILY OF MISSING GIRL NOT EXPECTING 'GOOD OUTCOME' AS FEDS SEARCH HOME

Photo of missing child Harmony Montgomery

Harmony Montgomery was placed in her father's custody just months before she was last seen. He had served time in connection with a violent drug robbery and was later accused of domestic violence by her stepmom. (Manchester Police)

"As I stated from the beginning of this investigation and throughout, every effort has been made to bring Harmony home to her family. Our commitment to bringing Harmony home has not wavered, nor will it. Bringing Harmony home will continue to be the number one priority for the Manchester Police Department," the police chief continued. 

MISSING HARMONY MONTGOMERY: TIMELINE OF NEW HAMPSHIRE GIRL'S DISAPPEARANCE

Montgomery went missing from her father’s custody in 2019, according to authorities, but a missing person report wasn’t filed until late last year when her noncustodial mother learned she had never been registered to attend school in her father’s hometown.

The adoptive father of Montgomery's little brother posted Thursday on Twitter that it's "nearly impossible and unjust to use words to describe how our family feels on this very sad day."

"Harmony should be enjoying the fun that kids experience each summer. Instead, we're all left with a depth of sadness that we struggle to accept or understand," Blair Miller said in a statement posted in his tweet. "Our son, Jamison, will forever be challenged with trying to understand the brutal and senseless loss of his sister." 

Harmony Montgomery is missing.

Anyone with information about Harmony Montgomery is asked to call the 24/7 tip line at 603-203-6060. (Manchester Police Department)

Adam Montgomery, the girl's father, has been held without bail since January on child abuse and other charges in connection with the case. His estranged wife and Harmony’s stepmom, Kayla Montgomery, has been charged with fraud and other charges after allegedly collecting food stamps in the girl’s name for months after she last saw her and again for lying to the grand jury.

ADOPTED FATHER OF HARMONY MONTGOMERY'S BROTHER PLEADS WITH GIRLS' FATHER FOR ANSWERS

side-by-side photo of Adam Montgomery and daughter Harmony Montgomery

Adam Montgomery, who police arrested on child abuse and endangerment charges in connection with an alleged assault on his daughter, Harmony. (Manchester Police)

In June, police returned to the former home where the young girl had lived with her father and stepmother and were seen collecting evidence such as an old refrigerator. 

The investigation is ongoing, and police are not making further comments at this time. 

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Officials are calling on anyone with information on the young girl and her murder to come forward by calling or texting a 24-hour tipline: 603-203-6060.

Fox News' Michael Ruiz contributed to this report.