German customs officials said on April 2 that they have halted a shipment to Iran of a general anesthetic drug that also is used to execute people by lethal injection.
The shipment of 2.5 kilograms of sodium thiopental had not received export clearance as required by law.
Sodium thiopental is the first of three components used on death-row convicts to induce coma and death.
The European Union, which opposes the death penalty, has restricted its export.
Amnesty International has reported a sharp rise in executions in Iran during 2011.
More than 600 reported executions there last year included nearly 300 credible reports of "secret" executions.
Iranian opposition leaders say the regime has increased executions to intimidate and silence the opposition from taking to the streets as they had done during the 2009 and 2010 Iranian election protests.
With reporting by Dpa, Europe online; haber monitor, and Amnesty International