U.S. lawmakers and foreign policy insiders are calling on the international community to re-open its “flawed” investigation into Iran’s past nuclear weapons research, according to conversations with multiple sources who say the extent of Iran’s past nuclear work is likely much larger than previously believed.

The calls to reinvestigate Iran’s nuclear work come on the heels of revelations by anonymous U.S. officials who said the Obama administration held onto evidence showing the Islamic Republic performed extensive nuclear weapons research—a finding that contradicts findings by international monitors and longstanding claims by Iranian officials.

Administration officials made no mention of the finding when International Atomic Energy Agency (IAEA) inspectors first discovered it in December, but now say the evidence is proof Iran worked to build nuclear weapons as recently as 2003.

The discovery has prompted lawmakers to demand that the IAEA re-open its currently closed investigation into Iran’s past nuclear weapons work.

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