The company is suspected of sending to Iran, via Turkey, machines for the manufacture of turbine propellers used in energy generation, the Finance Ministry said in a statement Monday.
The European Union and the United States have imposed sanctions on Iran over its nuclear program. They have targeted suspected export control violators dealing in so-called dual-use technology, which can have both civilian and military applications.
Tehran says its nuclear program is aimed at energy production but many Western countries fear it is a cover for weapons development.
Customs agents and police seized documents and made arrests at the company in Durango, some 400 kilometers (250 miles) north of Madrid, earlier this month, the statement said.
The machinery was worth almost €1 million ($1.29 million) and officials believe it went to a company in Istanbul before being sent on to Iran. Those arrested face smuggling charges, which carry punishments of up to six years in prison and a fine.
The statement gave no details about those arrested nor the names of the companies involved, and officials declined to elaborate.
The company requested an export license for the same machinery in 2009 but authorities turned it down, according to the statement.
