DAKAR, Senegal (AP) — It’s the largest piece of Mars ever found on Earth — a 54-pound (25-kilogram) meteorite that fetched more than $5 million at a New York auction last month, setting a world record.

But in the West African nation of Niger, where the rusty-red rock was unearthed in the Sahara Desert, officials have launched an investigation into what they call possible “illicit international trafficking,” claiming it may have been smuggled out of the country.

Here’s what to know about the meteorite and the legal dispute:

Sotheby’s said the rock, named NWA 16788, was blown off the surface of Mars by a massive asteroid strike and traveled 140 million miles (225 million kilometers) to Earth.

It was discovered in the Sahara in northwestern Niger by a meteorite hunter in November 2023, according to the auction house. His identity was not disclosed. Nor was the identity of the buyer last month.

Meteorite hunting is growing in arid Saharan countries like Niger. Though meteorites can fall anywhere on Earth, the Sahara has become a prime spot for their discovery in part due to the favorable climate for their preservation.

Hunters often search for space rocks that can be sold to collectors or scientists. The rarest and most precious are from Mars and the moon.

According to the Heritage academic journal, the rock was sold to an international dealer before it ended up in a private galley in Italy. A team of scientists from the University of Florence examined the rock last year to learn more about its structure and where it came from before falling to Earth, the publication said.

The meteorite was also briefly on display in Rome before it was next seen in public in New York last month during the auction.

Following the sale, Niger raised questions about how the meteorite came to be sold at auction.

Niger's government announced an investigation last month to determine the circumstances of the meteorite's discovery and sale, saying in a statement it was “akin to illicit international trafficking.”

Last week, President Abdourahamane Tiani suspended the export of “precious stones, semiprecious stones and meteorites nationwide” in an effort to ensure their traceability.

Sotheby's said in a statement sent to The Associated Press the meteorite was exported from Niger and transported in line with all relevant international procedures.

“As with everything we sell, all necessary documentation was in order at each stage of its journey, in accordance with best practice and the requirements of the countries involved." the statement read.

Authorities in Niger did not respond to AP questions.

Patty Gerstenblith, a cultural heritage lawyer and expert on illicit trade, said that under the UNESCO convention on cultural property — which Niger and the U.S. have ratified — rare minerals, like meteorites, can qualify as cultural property.

However, Gerstenblith said Niger needs to be able to prove it owned the meteorite and that it was stolen, as illegal export from the country does not make the meteorite illegal in the U.S.

“If the meteorite was not stolen and if it was properly declared upon import into the U.S., then it would not seem that Niger can recover the meteorite,” she told the AP.

Paul Sereno, a paleontologist who has spent years uncovering dinosaur fossils in Niger’s Sahara, is campaigning to return the country’s cultural and natural heritage — including meteorites.

“When you have laws that clearly say rare minerals like meteorites are cultural artifacts, you cannot simply come in an take something that is so unique and valuable to a country,” he told the AP.

“We’re just not in the colonial area anymore,” he added.

Some countries, like Morocco, one of the leading sources of meteorites on the international market, require restitution if the objects are discovered on their territory. But enforcement has been challenging due to the vast desert areas and informal trading networks.