Fox News has exclusively obtained satellite imagery revealing what an opposition group says is a previously undisclosed Iranian nuclear weapons facility – raising fresh concerns amid ongoing negotiations between Tehran and the Trump administration.

The newly identified site, located in Iran’s Semnan Province, is far from the regime’s already-known nuclear facilities. According to the National Council of Resistance of Iran (NCRI), intelligence gathered from sources inside the country points to a sprawling compound covering nearly 2,500 acres.

Code-named the “Rainbow Site” by Iranian officials, the facility has reportedly been in operation for more than a decade, masked as a chemical production company known as Diba Energy Siba.

Satellite images reveal the location and layout of an alleged Iranian secret nuclear weapons facility that has been unknown until now. (National Council of Resistance of Iran)

“Without prejudging the negotiation, I will say, so far so good,” Vance told reporters. “We’ve been very happy with how the Iranians have responded to some of the points that we’ve made.”

The discovery of the Rainbow Site could complicate the already delicate diplomacy surrounding Iran’s nuclear capabilities and the possibility of a renewed agreement.