IAEA inspectors verified that modern Research and Development (R+D) centrifuges "were accumulating, or had been prepared to accumulate, enriched uranium, Efe news reported on Wednesday.
Since May, Iran has been gradually violating the JCPOA to exert pressure on European countries to guarantee the economic advantages set out in the agreement.
The deal was abandoned by the United States in 2018.
First of all, Iran began to accumulate more enriched uranium than it was allowed to (300 kilos), and then it exceeded the purity of enriched uranium set out in the JCPOA.
The latest violation relates to the R+D program for a new generation of centrifuges, which are much faster and more efficient than those used until now.
According to the JCPOA, Iran can only carry out R+D work for a decade within a limited framework and it cannot accumulate enriched uranium.
In addition to accumulating uranium in these facilities, Iran has announced it will install new centrifuge cascades with other types of machine, the IAEA inspectors said in their report released Thursday.
These centrifuges are more advanced and faster than the conventional IR-1 type, of which Iran has 5,060 in Natanz and another 1,000 installed at its Fordo underground plant.
The JCPOA is at risk of failing since the United States withdrew from it last year and imposed new sanctions on Iran.
Tehran reacted by violating the agreement and demanding that the European signatory countries guarantee the economic benefits that the pact laid out.
The agreement places significant limitations on Iran's nuclear program to prevent the country from making atomic bombs.
In return, international sanctions against the country were lifted and economic normalization was promised.
But has been thrown into question after the US applied fresh punitive measures, especially against the country's oil sector.
( With inputs from IANS )