The first clear pictures of Iran’s nuclear site near Isfahan have been published and analyzed following an explosion at or near the site on Nov. 28, and they provide another piece of the puzzle. But what happened there remains a mystery.

Iran’s uranium conversion facility sits outside Isfahan. It is there that yellowcake is turned into uranium hexafluoride gas (UF6), which is then fed into centrifuges and turned into enriched uranium. The enriched uranium then can be made into fuel for power stations, or it can be highly enriched for a nuclear bomb.

Fox News obtained satellite pictures of the Isfahan nuclear site between Dec. 3 and 5, less than a week after reports of explosions in the area were heard. Analysts at the Institute for Science and International Security (ISIS), which employs some of the most widely respected experts on Iran’s nuclear sites, scrutinized the images and said there is no evidence of an explosion -- but there wouldn’t be clear evidence several days after an event.

Click here to view the ISIS report.

Iranian officials have issued conflicting comments about the blast, which, if it occurred at the uranium conversion facility, could be very damaging to the nation’s nuclear program.

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A report of the explosion was first mentioned in the semi-official Fars News website. Then the report was removed. Then it was finally described as an explosion deriving from a military exercise by Isfahan’s governor, Alireza Zaker-Isfahani.

Israeli sources have suggested that the blast occurred at the nuclear facility; Iran, in turn, has denied that any sort of blast happened there.

But others find Iran’s denials suspicious, given that there have been numerous acts of sabotage against its nuclear and military sites and scientists in the last few years. Just last month, an explosion occurred at a sensitive missile site, killing 20 people, including the father of Iran’s Shahab 3 missile. It is not clear what caused that blast, or whether it was accidental, but many believe it was no coincidence.

ISIS analysts who looked at the images from Isfahan said there had been a dramatic change in the landscape around a tunnel leading down to a storage facility on the periphery of the uranium conversion site. Several structures above that storage facility, which had been there for 15 years and stood intact as recently as August, are gone. There now is evidence of bulldozing around the old structures.

It is not clear what is stored in that facility, which used to be a salt mine, or whether the underground storage was damaged. But Iran has been known to store UF6 underground, ISIS says, so it is possible that converted yellowcake was in that facility. According to ISIS, there is no evidence of an explosion, but there wouldn’t be clear evidence several days after an event.

“After five to seven days, that’s what you would be looking at anyway — clean-up,” ISIS senior analyst Paul Brannan told Fox News.

“The pictures we have seen were dramatic insofar as the buildings were there for at least 15 years,” he said. “On Dec. 5, they were gone. Whether or not that is circumstantial is not clear, but it warrants further scrutiny.”

Brannan says much of Iran’s yellowcake has been converted to UF6, but the Iranians still have some stock. Beyond that, however, the nation’s ability to mine and mill yellowcake is limited.

“There is something strange going on,” he said. “It is not clear what it is. There was the recent blast at the missile facility with people killed. There was a report of a blast at Isfahan’s uranium conversion site. A U.S. drone has been downed.

“Something is going on. It’s not clear what it is.”

Amy Kellogg currently serves as a Senior Foreign Affairs Correspondent based in the London bureau. She joined Fox News Channel (FNC) in 1999 as a Moscow-based correspondent. Follow her on Twitter: @kellogglondon