The International Atomic Energy Agency (IAEA) revealed that Iran is now enriching uranium with advanced centrifuges in violation of the Joint Comprehensive Plan of Action (JCPOA). An IAEA report verified that two R&D lines at Iran's Natanz facility, each of which contains up to 20 centrifuges, "were accumulating, or had been prepared to accumulate, enriched uranium." The Agency also reported that Iran is in the process of installing 164-machine cascades of IR-4 and IR-2m models, both of which were removed under the JCPOA. Iran informed the IAEA in a letter on September 25 of the additions, which also include a 165-machine cascade of IR-6 centrifuges. Under the terms of the JCPOA, Iran can only use first-generation IR-1 centrifuges at Natanz, with a small number of more advanced models allowed for research purposes.