The Associated Press revealed that satellite images analyzed by experts show intensified construction of a massive new structure within a key facility of Israel’s long-suspected nuclear weapons program. Experts believe the facility could be a new reactor or a nuclear weapons assembly site, but the secrecy surrounding the program makes it difficult to confirm.

The ongoing work at the Shimon Peres Nuclear Research Center in the Negev desert near the city of Dimona raises questions about Israel’s status, widely believed to be the only country in the Middle East possessing nuclear weapons. It may also spark international criticism, especially since it follows Israeli and US strikes on nuclear sites in Iran in June over concerns that the Islamic Republic might use its enrichment facilities to make a nuclear weapon, including the heavy water reactor at Arak.

Seven experts spoke to the Associated Press after examining the images and all confirmed the construction is related to Israel’s nuclear program due to its proximity to the Dimona reactor, which does not have a civilian power station. However, they were divided on the nature of the new construction: three believed the site, its size, and multiple floors indicate the most likely possibility is a new heavy water reactor capable of producing plutonium and other materials essential for nuclear weapons manufacturing.

The other four considered it might indeed be a heavy water reactor but also possibly a nuclear weapons assembly facility, recommending caution before making a final judgment given the early construction stages.

Jeffrey Lewis, an expert at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies, said, “It is likely a reactor. This judgment is provisional but typical for such matters. It’s very hard to imagine it being something else.” Israel neither confirms nor denies possessing nuclear weapons, and its government did not respond to requests for comment, nor did the White House, Israel’s closest ally.

The Associated Press had previously revealed in 2021 excavation operations at the facility about 90 kilometers south of Jerusalem. Satellite images then showed a pit 150 meters long and 60 meters wide near the original heavy water reactor.

Images taken on July 5, 2025, by Planet Labs showed accelerated construction at the site, with thick concrete walls apparently being built on multiple underground floors, while cranes rose above.

So far, no containment dome or other components usually accompanying a heavy water reactor appear, but these could be added later, or the reactor might be designed without them.

The current Dimona reactor, which began operating in the 1960s, has far exceeded the typical lifespan of reactors from that era, indicating a need for replacement or upgrade soon.

Lewis said, “It is tall, which you expect because the reactor core will be very long. Based on location, size, and the general lack of other construction on site, it is most likely a reactor rather than anything else.”

Edwin Lyman, a nuclear energy expert at the Union of Concerned Scientists in the US, said the new construction might be a square-shaped reactor without an obvious containment dome but confirmed that the lack of transparency makes certainty difficult.

He added, “Israel does not allow any inspections or international verification, forcing the public to guess.”

Details of Dimona remain highly guarded secrets in Israel, but a whistleblower in the 1980s leaked images and information leading experts to believe Israel produced dozens of nuclear warheads.

Daryl Kimball, executive director of the Arms Control Association in Washington, said, “If it is a heavy water reactor, it means they seek to maintain the ability to produce spent fuel that can later be processed to separate plutonium for more nuclear weapons, or they are building a facility to maintain their arsenal or manufacture additional warheads.”

Israel is believed, like India and Pakistan, to rely on heavy water reactors to produce its nuclear weapons. These reactors may be used for scientific purposes, but the plutonium they produce is a key ingredient in nuclear bombs, and the tritium produced can be used to boost nuclear warhead power.

Israel surrounds the Dimona reactor with complete secrecy, but leaks in the 1980s revealed details and images of the facility, prompting experts to conclude Israel may have produced dozens of nuclear warheads. The Bulletin of the Atomic Scientists estimated in 2022 that Israel possesses about 90 nuclear warheads.

Israel is believed to have started building the nuclear site in the desert in the late 1950s after a series of wars with its Arab neighbors since its founding in 1948 following the Nazi Holocaust. Pursuing a policy of nuclear ambiguity helped deter its enemies. It is among nine countries believed or known to possess nuclear weapons, and only four have not joined the Nuclear Non-Proliferation Treaty, the key international agreement to prevent the spread of nuclear weapons. This means the International Atomic Energy Agency has no inspection rights at Dimona.

When asked about the ongoing construction, the International Atomic Energy Agency in Vienna confirmed that Israel “is not obligated to provide information about any other nuclear facilities in the country” outside the Soreq research reactor.