The mother of a murdered child discovered a Barbie doll at her gravesite 23 years ago and kept it in a glass case until now

It has been more than 20 years since a 6-year-old girl was kidnapped from her Salt Lake City home, sexually assaulted and killed.

Rosie Tapia’s body was found in a canal off the Jordan River several hours after she disappeared, but her case was never solved.

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Now, 23 years later, the Utah Cold Case Coalition is asking the public for any tips related to a Barbie doll, which was found on top of the girl’s grave shortly after she died in 1995.

“Rosie’s mother went back to her grave regularly,” Karra Porter, co-founder of the nonprofit Utah Cold Case Coalition, tells PEOPLE. “She went back and found this doll on there, which was a bit unusual and kept it in a glass case this whole time.”

In September 2017, the coalition approached the Salt Lake City Police Department with the doll and asked them to test it for DNA, but Porter says it didn’t get a response. (Attempts to reach the police department were unsuccessful.)

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There has been a history of friction between Tapia’s family and law enforcement, according to a 2017 article in the Salt Lake City Tribune, but Sgt. Brandon Shearer said investigators continued to investigate the case.

“We have met with the Tapia family regularly throughout this investigation and will continue to meet with them regularly,” Shearer told the publication.

Since then, the coalition decided to move forward on testing the doll without assistance from law enforcement. Porter says there are two phases in the test. The first phase extracts the DNA, and the second — and more costly — phase identifies the DNA.

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Last year, the group paid to get the DNA extracted from the doll, which included male DNA, Porter says. The group believes the doll, known as Pretty Hearts Barbie, could be a valuable clue in the case and they’re hoping someone will come forward with any information on who may have left it there.

“We thought we’d give the public a chance to say, ‘I left that there,’ or ‘Hey, that was my doll. It went missing. Now I know where it is,'” Porter says.

According to Porter, they have received numerous calls about Barbie dolls left at grave sites for other murdered girls, including some in other states. She didn’t know if there was a link between the cases.

“The time frames we’ve been contacted on are fairly close together although in different states,” she says. “Could it be the same person? I don’t know. Could it be a certain type of predator? I don’t know. It could also be totally innocent.”