An Iranian national was caught by the Trump administration attempting to smuggle materials that can be used to enrich uranium, the key component in a nuclear weapon, out of the U.S., according to the Justice Department.

Behzad Pourghannad allegedly attempted to smuggle carbon fiber out of America and ship it to Tehran. Pourghannad was arrested in May 2017 in Germany and later extradited to the U.S. He arrived in America on Monday. On Tuesday, the Justice Department unsealed a three-count indictment charging Pourghannad and two others in the plot to export the sensitive nuclear materials.

Ali Reza Shokri and Farzin Faridmanesh, the two alleged conspirators, remain at large.

"Pourghannad is alleged to have sought to procure for Iran large amounts of carbon fiber—a commodity that can be used in the enrichment of uranium," Assistant Attorney General Demers said in a statement. "U.S. sanctions exist to prevent behavior, like this, which endangers our country, and the Department is committed to vigorously enforcing them. Pourghannad and others who would attempt to thwart these laws need to know that their actions, which benefit Iran’s destabilizing efforts and make Americans less safe, will not go unpunished."

The carbon fiber material could be used by Iran to fuel its ongoing enrichment of uranium, which has emerged as a flashpoint in the latest standoff between the Trump administration and Iran. Following a bevy of new sanctions by the U.S., Iran publicly breached restrictions on the amount of enriched uranium it can stockpile inside the country.

"Carbon fiber has many aerospace and defense applications, and is strictly controlled to ensure that it doesn't fall into the wrong hands," U.S. Attorney Geoffrey Berman said in a statement. "Pourghannad and his co-defendants allegedly went to great lengths to circumvent these controls and the United States' export laws. Together with our law enforcement partners, we will continue to protect our nation's assets and protect our national security."

The case is part of a larger effort by the Trump administration and its law enforcement agencies to crack down on Iran's illicit procurement of sensitive technology and nuclear materials.

"This case shows the FBI aggressively pursues those who break the law and violate sanctions against Iran," FBI Assistant Director John Brown, of the counterintelligence division, said in a statement.

"Iran remains determined to acquire U.S. technology with military applications, and the FBI is just as determined to stop such illegal activity," Brown said. "The charges against these three Iranian nationals, and the extradition of Mr. Pourghannad, demonstrate we take Iran's actions extremely seriously and will work with our partners to defeat them."

FBI officials said they would continue to pursue Iranian agents and other who work to help Iran continue its most sensitive nuclear research, including its weapons program.

"If you aid Iran in its efforts, you will be held accountable," FBI Assistant Director in Charge William Sweeney said in a statement.

The plot to illicitly export the carbon fiber from the U.S. began in 2008 and continued into 2013, according to the Justice Department.

"Between 2008 and July 2013, Pourghannad, Shokri, and Faridmanesh lived and worked in Iran," according to information provided by the department. "During that period, they worked together to obtain carbon fiber from the U.S. and surreptitiously export it to Iran via third countries. In particular, Shokri worked to procure many tons of carbon fiber from the U.S."

"Pourghannad agreed to serve as the financial guarantor for large carbon fiber transactions; and Faridmanesh agreed to serve as the trans-shipper," the DOJ alleged. "Carbon fiber has a wide variety of uses, including in missiles, aerospace engineering, and gas centrifuges that enrich uranium."