The images, taken by satellites that belong to ImageSat International (ISI) on April 29, show the entrance gate leading to the tunnels of the enrichment site open, which is unusual.
The images also show some 30 vehicles and four buses parked outside on April 29, something that hasn't happened in months.
The underground facility is located inside a mountain and is meant to be under supervision of the International Atomic Energy Agency (IAEA).
According to ISI, the Israeli satellite AROS-B showed the site, which appear to be vacant for the past two years, is now seemingly active again.
The photos also show that progress has been made on some structures being built outside the facility. For comparison, ISI also released satellite images from July 2016 of the same place.
These structures are believed to be meant for production, research and development work.
The images were released just three days after Prime Minister Benjamin Netanyahu presented documents and images
that he said proved that Tehran had lied “big time” to world powers about its military nuclear program.
The Israeli intelligence agency Mossad was able to smuggle half a ton of documents—some 55,000 physical documents and an additional 50,000 files on CDs—from Tehran. These documents, according to Israel, make up a significant portion of Iran's nuclear archive.