An unidentified girl whose remains were found in a suitcase in Texas three years ago was likely from Arizona, the National Center for Missing and Exploited Children said on Wednesday.

Officials said that Tuesday marked three years since the girl's remains were found in a black suitcase at the edge of a pasture off an interstate between Houston and Dallas. In that time, no one has stepped forward to identify her.

The group cited pollen analysis of the remains in efforts to identify the girl, whose remains were found by a man mowing grass near Madisonville, Texas.

The girl, known only as “Madisonville Jane Doe,” was believed to be between 2 and 6 years old and was found wearing a pink dress; she also wore a diaper and had a feeding tube, which would have been surgically implanted, authorities said, adding that she was found wrapped in garbage bags.

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Medical experts believe she likely had a condition called micrognathia, which would have affected her ability to eat on her own.

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Authorities said the girl was likely dead for three to five months before she was found. Forensic experts believe the girl was Caucasian or Hispanic and had thick, dark hair. Genealogy research revealed she also had Native American lineage.

“It’s normal for anyone who has compassion to be bothered by this case. This is a young child,” Madison County Sheriff Travis Neeley said, according to a National Center for Missing and Exploited Children blog post. The death was ruled a homicide.

He said that “these kinds of cases are the worst kind,” adding that “they're frustrating because you feel helpless. I mean, I cannot bring nobody back to life by no means, but I want to bring some kind of peace, if nothing else.”

Neeley, who is planning to retire from his 20-year law enforcement career, said he is determined to solve the mystery of the little girl before he steps down.

While the girl was found in Texas, the pollen analysis suggests she was from the southwest U.S. or the adjacent region in Mexico. It's even more likely she was from southeast Arizona, officials said.

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Forensic artists created a facial reconstruction image using a CT scan of her skull to help identify the girl.