Iraqi boys lift wreckage from a crater created by a roadside bomb in 2008. (Essamal-Sudani/AFP/Getty Images)

Radio frequency modules made in the United States ended up in the detonation systems of roadside bombs targeting coalition forces in Iraq, according to the Justice Department, which unsealed an indictment Tuesday describing the illegal export of the devices to Iran.

The department said it is seeking the extradition of four men who were arrested Monday in Singapore. The department said the men, all citizens of Singapore, falsely told the Minnesota-based firm that made the modules that the parts were for a telecommunications project in Singapore.

The Justice Department said that after the modules arrived in Singapore, they were forwarded to Iran by air freight through third countries.

Charged in the indictment are Wong Yuh Lan, Lim Yong Nam, Lim Kow Seng and Hia Soo Gan Benson. The indictment, which was returned last month and unsealed Tuesday, also charges Hossein Larijani, an Iranian citizen, who remains at large. Larijani owned a company in Singapore, Opto Electronics, and another in Tehran, Paya Electronics Complex.

The indictment alleges that the Singaporeans negotiated a price of $69.30 for each module and billed the Iranian company $85 per module, or $510,000 for the order of 6,000 modules.

The men, along with associated companies, were charged with conspiracy to defraud the United States, smuggling, illegal export of goods from the United States to Iran, false statements and obstruction of justice. They face up to 20 years in prison if convicted.

The Commerce Department on Tuesday announced that it is adding to its Entity List various people and companies in China, Hong Kong, Singapore and Iran that were allegedly associated with the conspiracy. That action essentially bars U.S. companies from exporting to them.

“This case underscores the continuing threat posed by Iranian procurement networks seeking to obtain U.S. technology through fraud,” said Lisa Monaco, assistant attorney general for national security.

Justice Department officials said the alleged conspiracy is the ninth case involving the illegal export of U.S. technology to Iran since June.

The Minnesota company, which is not accused of any wrongdoing, exported the 6,000 modules in four shipments in 2007 and 2008. Between 2008 and 2010, the U.S. military found the devices in 16 makeshift bombs.

“This is the first prosecution in which the government has alleged that it has the evidence to trace — by serial number — specific components exported from the United States to Iran, and later to IEDs in Iraq,” said Dean Boyd, a Justice Department spokesman.

A law enforcement official, who spoke on the condition of anonymity to discuss the case candidly, said that investigators “can’t say for sure” whether any of the remaining devices were used in bombs that killed or wounded U.S. troops.

The indictment notes that about 60 percent of American combat casualties in Iraq between 2001 and 2007 were caused by makeshift explosives.

The modules, ordinarily used in wireless local area networks, have an encryption capability and can transmit data wirelessly up to 40 miles when configured with certain antennae.

The indictment also charges three of the Singaporean men with a separate fraud conspiracy involving an attempt to acquire two types of military antennae from the United States.

In January 2010, the Commerce Department placed Larijani’s Singapore company on its Entity List, and Larijani repeatedly called officials in Washington to complain, according to the Justice Department.