Four men have been arrested in Germany charged with delivering valves for a heavy-water reactor to Iran.

The four men, one German and three that hold dual German-Iranian citizenship, were arrested at their homes in Hamburg, Oldenburg and Weimar last week, and their homes and offices were reportedly searched by customs officers, Reuters reports.

Prosecutors announced on Wednesday: “In 2010 and 2011, the suspects are believed to have helped in the delivery of special valves for the construction of a heavy-water reactor in Iran and, therefore, to have broken the Iran embargo.”

Iran is building a heavy-water research reactor near the central town of Arak.

The exporters have reportedly used a firm based in Turkey and Azerbaijan to circumvent the embargo restrictions.

Experts claim that sanctions on Iran have slowed down the Iranian nuclear program.

Iran rejects all suspicions about its nuclear activities, insisting that as an NPT signatory it has a right to exploit nuclear power for peaceful purposes, which, according to the Islamic Republic is the only target of its nuclear program.