Well before the Vela incident, American intelligence agencies had made the assessment that Israel probably possessed its own nuclear weapons.[31] According to journalist Seymour Hersh, the detection was the third joint Israeli-South African nuclear test in the Indian Ocean, and the Israelis had sent two IDF ships and "a contingent of Israeli military men and nuclear experts" for the test.[32] Author Richard Rhodes also concludes the incident was an Israeli nuclear test, conducted in cooperation with South Africa, and that the United States administration deliberately obscured this fact in order to avoid complicating relations with South Africa and Israel.[33] Likewise, Leonard Weiss offers a number of arguments to support the test being Israeli, and claims that successive U.S. administrations continue to cover up the test to divert unwanted attention that may portray its foreign policy in a bad light.[34] Similarly, Professor Avner Cohen concluded that in hindsight, the existence of a cover-up by the United States is unambiguous because there were “at least three independent scientific pieces of evidence unrelated to a satellite that confirm the existence of the explosion.”[35] [36]
In the 2008 book The Nuclear Express: A Political History of the Bomb and its Proliferation, Thomas C. Reed and Danny B. Stillman stated their opinion that the "double flash" was the result of a joint South African–Israeli nuclear bomb test.[37] David Albright stated in his article about the "double flash" event in the Bulletin of the Atomic Scientists that "If the 1979 flash was caused by a test, most experts agree it was probably an Israeli test".[2] In 2010, it was reported that, on 27 February 1980, President Jimmy Carter wrote in his diary, "We have a growing belief among our scientists that the Israelis did indeed conduct a nuclear test explosion in the ocean near the southern end of Africa."[38]
Leonard Weiss, of the Center for International Security and Cooperation at Stanford University writes: "The weight of the evidence that the Vela event was an Israeli nuclear test assisted by South Africa appears overwhelming."[39]
Reed has written that he believes the Vela incident was an Israeli neutron bomb test.[40] The test would have gone undetected as the Israelis specifically chose a window of opportunity when, according to the published data, no active Vela satellites were observing the area. Although the decade-old Vela satellite that detected the blast was officially listed as "retired" by the U.S. government, it was still able to receive data. Additionally, the Israelis chose to set off the test during a typhoon.[41] By 1984, according to Mordechai Vanunu, Israel was mass-producing neutron bombs.[42]