Newly released satellite images of Iran’s top-secret Parchin military complex reveal that even as Iran was working to negotiate a nuclear deal, it was apparently working to hide its atomic work of the past and hedge its bets for the future.

Forecasting site Stratfor.com says the images published Monday show Iran building a tunnel into a heavily guarded mountain complex inside the Parchin facility, some 20 miles southeast of Tehran, while also working to erase signs of alleged high-explosive testing at another area on the site.

“We’re not saying they’re cheating on the nuclear deal,” Stratfor analyst Sim Tack told The Daily Beast. “The images show Iran was going through the motions to hide what it’s done before, and it is still…developing facilities that the IAEA may or may not have access to,” Tack said, referring to the International Atomic Energy Agency.

The progression of satellite images tracking construction at Parchin from 2012 to 2015 show how Iran’s leaders apparently worked to keep regime hardliners happy by moving forward with weapons programs, even as the leadership worked to erase signs of an illegal nuclear weapons program, Tack said.

The satellite images appear to show new paving around the building that was alleged to be a test site for high-energy explosive charges used to detonate a nuclear weapon. Comparing satellite images from 2010 to one taken this year, Tack points out that the area has been paved, and plants and trees surrounding it removed and the soil scraped—all steps one would take to hide the radioactive fallout of nuclear weapons testing.

The IAEA sent a team to inspect the site last fall, one of the final steps up to the adoption of a deal that will give the country tens of billions of dollars in sanctions relief.

“In September, IAEA Director General [Yukiya] Amano visited the inside of the suspected explosives test chamber building, and found it had been emptied,” said Andy Weber, former Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs. He added that in his opinion, Stratfor’s analysis “tracked well with the photos.”

While the destruction of that controversial building has been reported before, Tack said the publication of images of the near-simultaneous construction of the tunnel entrance to another part of the complex is new.

“The imagery showed they were working on a tunnel entrance within the Parchin complex…and it looks like it’s complete,” Tack said. A 2014 image Stratfor did not release showed construction equipment outside tunnel entrance.

“They were still going forward with that construction during the talks,” he said.

The mysterious subterranean complex could be part of Iran’s ballistic missile program that triggered new U.S. sanctions in January, even as the nuclear sanctions were being lifted. The U.S. first detected that Iran was testing missile engines at the site in 1997.

Parchin was also the site of a large explosion in 2014 that the Iranian government never explained.

“It could have come from a test of rocket fuel or conventional warheads,” Tack said.

Whatever’s hidden beneath that mountain, the IAEA didn’t get a look at it last September, he said.

“There are places where nobody knows what’s going on,” he said.

The IAEA declined to comment on the new satellite photos.

The Iran’s U.N. Mission did not respond to requests for comment.

Iran has dismissed questions about suspicious construction at Parchin before. The Iranian official news agency IRNA reported that when IAEA chief Amano inspected the facility, he “visited construction works at Parchin, about which there are some irrelevant claims.”

Obama administration officials would not comment on what the photos show, but insisted that IAEA inspectors can check it out if they see fit.

A senior Obama administration official said the nuclear deal, known by the cumbersome acronym JCPOA, for Joint Comprehensive Plan of Action, “means the IAEA will have the access it needs to any suspicious location going forward. Such transparency will ensure that these past activities will not occur again, and if they do, that they will be quickly detected.”

The official spoke on condition of anonymity to defend a deal that is described as the cornerstone of President Barack Obama’s foreign policy legacy.