Police in Boulder, Colorado, will consult with a state cold case team as they continue to investigate the 1996 murder of 6-year-old JonBenet Ramsey.

Authorities have received more than 21,000 tips, letters and emails about the case, and have traveled to 19 states to speak with more than 1,000 people, but the murder remains unsolved.

“This crime has left a hole in the hearts of many, and we will never stop investigating until we find JonBenet’s killer,” Police Chief Maris Herold said in a news release Wednesday ahead of the 26th anniversary of JonBenet’s death.

The Colorado Cold Case Review Team is made up of professional investigative, analytical and forensic experts from across the state. Police said the team “is another tool to help further cold case homicide investigations.”

JonBenet was found beaten and strangled to death on Dec. 26, 1996, in the basement of her family’s Boulder home. At the time, the only other people known to be in the home were her parents, Patsy and John, and her brother, Burke.

No one has ever been charged in the case.

Police have often been criticized for their initial handling of the investigation, and earlier this year JonBenet’s father showed support for an online petition that asked the governor to intervene by putting an outside agency in charge of DNA testing.

Theories have swirled for years that JonBenet, who spent much of her life in the beauty pageant circuit, was either killed by an intruder who broke into the house or by a member of her family. Initially, the Ramseys were reluctant to be interrogated by police or to allow their then-9-year-old son to be questioned.

In 2008, then-Boulder District Attorney Mary Lacy officially cleared them based on DNA test results. In a letter of exoneration, she said evidence showed an unknown male’s DNA on JonBenet’s underwear and long johns.

However, her findings came into question following a joint investigation by NBC affiliate KUSA of Denver and the Boulder Daily Camera. In 2016, the news outlets had forensic experts examine the evidence Lacy reviewed as well as reports from a private lab that tested the DNA, and said the experts questioned whether the DNA belonged to a single, unidentified male.

Lacy told ABC News that same year that she stood by her decision to clear the family.

Federal, state and local law enforcement agencies continue to work on JonBenet’s case. Boulder police have also sought help from several private DNA laboratories across the country, the news release states, noting that the “amount of DNA evidence available for analysis is extremely small and complex.”

Police said whenever new technology becomes available, the department will have the samples tested.

JonBenet’s half-brother, John Andrew, commented on the news, writing on Twitter that it was a “positive” step in her case.

“Forward progress. More work to be done to catch a killer but it can be done,” he tweeted.