One of the four known pairs of ruby slippers worn by Judy Garland in the 1939 film “The Wizard of Oz” was recovered 13 years after it was stolen from a Minnesota museum, officials said Tuesday.

"We reached the first goal, the recovery, and it's a great day," North Dakota Attorney Christopher Myers said. "But we're not done."

The slippers, which were said to be one of the most valued props in movie history, were recovered by the FBI in a sting operation. They were stolen in 2005 from a museum dedicated to the actress in her hometown of Grand Rapids, Minnesota, by someone who broke into the building through a window late at night.

'Wizard Of Oz' Ruby Slippers Recovered
A pair of ruby slippers featured in the classic 1939 film "The Wizard of Oz" is shown after it was recovered in a sting operation conducted in Minneapolis earlier this summer by the FBI, Sept. 4, 2018. Reuters/FBI Handout

The slippers, seized in an undercover operation in Minneapolis, were unveiled at a press conference held Tuesday. The FBI said the recovery was made due to a “credible” tip they received last summer. After a year-long investigation, the ruby slippers were finally recovered in July.

The pair was compared to another set of slippers kept at the Smithsonian's American history museum in Washington D.C. to verify its authenticity.

The FBI said the investigation into the people responsible for the 2005 theft is still continuing. According to reports, there are “multiple suspects” in the case.

"We've gathered lots of information on this case. We believe there's lots more to give," FBI special agent Joan Sanborn said.

Hollywood memorabilia collector Michael Shaw had given the slippers as a loan to the Judy Garland Museum in Grand Rapids, Minnesota, for their annual “Wizard of Oz” festival in 2005. The slippers were insured for $1 million at the time of the robbery. But according to experts, their worth could be twice that amount now, reports said.

'Wizard Of Oz' Ruby Slippers Recovered
A close up image shows details of the ruby slippers featured in the classic 1939 film "The Wizard of Oz" and stolen from the Judy Garland Museum in Grand Rapids, Minnesota, after it was recovered in a sting operation conducted by the FBI, Sept. 4, 2018. Reuters/FBI Handout

An unidentified person or group broke into the museum and stole the slippers from a small display case. Though an alarm was triggered, a signal was not sent to alert the police. There were no fingerprints or footprints of those who stole the slippers at the museum, and the security cameras were reportedly not working at the time of the incident.

“The biggest thing that ever happened to our museum was getting the slippers stolen,” museum co-founder Jon Miner said in 2015. “We were literally crying.”

"The thieves not only took the slippers, they took a piece of history that will be forever connected to Grand Rapids and one of our city's most famous children," Grand Rapids Police Chief Scott Johnson said.

An anonymous donor offered a $1 million reward for information regarding the whereabouts of the slipper and the thief's name in 2015.

"There's a certain romance in these types of schemes, sometimes sophistication, but at the end of the day it's a theft," Myers said. "These types of offenses not only deprive the owner of their property but all of us. … This type of cultural property is important to us as a society. It reflects culture, it holds our memories, it reflects our values."

The two other pairs of slippers belonging to Dorothy, the character played by Garland in the film, are held by the Academy of Motion Picture Arts & Sciences, and a private collector. The slippers were made from a dozen materials like wood pulp, silk thread, gelatin, plastic, and glass. The ruby color of the shoe came from the sequins and the red glass beads in the bows of the slipper.

The film was a classic adored by many. It won multiple Academy Awards, including the Oscar for best picture and best cinematography.