Ali Kourani, 32, of the Bronx, New York, and Samer el Debek, 37, of Dearborn, Michigan, were arrested and charged last week by the Department of Justice with providing material support to Hezbollah's Islamic Jihad Organization, the IJO.
Details of the accusations against them were revealed in criminal complaints made public in Manhattan federal court on Thursday.
Hezbollah, which has roots in Lebanon, is considered a terrorist organization by the United States. The IJO wing of the group is "responsible for the planning, preparation and execution of intelligence, counterintelligence and terrorist activities," officials said.
Kourani, who came to the United States in 2003 with a Lebanese passport and became a citizen in 2009, is accused of being in contact with Hezbollah between 2002 and 2015, and of attending a 45-day Hezbollah "boot camp" in Lebanon at age 16.
According to the criminal complaint against him, Kourani described his role with IJO as a "sleeper." These undercover operatives were supposed to "maintain ostensibly normal lives but could be activated and tasked with conducting IJO operations," the complaint said.
Kourani was a student in the United States and received a bachelor's in biomedical engineering in 2009, the year after he was officially recruited by Hezbollah, officials said.
For the IJO, Kourani looked for weapons suppliers in the United States to support IJO operations, gathered information about security operations at New York airports and surveilled numerous US military and law enforcement buildings in Manhattan and Brooklyn, the complaint said.
Kourani traveled between the United States and Lebanon almost once a year, and in 2011, he attended military training in Lebanon, the complaint said.
El Debek, also a naturalized US citizen, was recruited by Hezbollah in late 2007 or early 2008, according to the Justice Department, which said he conducted multiple covert operations in Panama and Thailand, but his home base continued to be the United States.
El Debek traveled to Panama twice for Hezbollah, once in 2011 and again in 2012, officials said. On his first trip, he located the US and Israeli embassies, gathered information about the security procedures at the Panama Canal and the Israeli Embassy and located hardware stores where explosive materials could be bought, according to the Justice Department.
On the second trip, he focused on the Panama Canal, finding areas of weakness in its construction and trying to figure out how close someone could get to the ships passing through it, the Justice Department said.
In 2009, el Debek traveled to Thailand to clean up leftover explosive material in a Hezbollah house the organization believed was under surveillance, according to the Justice Department.
Between 2008 and 2014, el Debek traveled from the United States to Lebanon to receive military training from Hezbollah multiple times, and he was extensively trained in "the creation and handling of explosives and explosive devices," the Justice Department said.
El Debek was trained to make landmines and other explosives, officials said. Part of that training taught him how to "gather many of the chemicals necessary to create an explosive device," a number of which were readily available in hardware stores, the complaint said.
Kourani has been charged with eight counts and el Debek has been charged with seven. The charges against both men include providing, attempting and conspiring to provide material support to Hezbollah. Multiple counts have a penalty of up to 20 years in prison.
CNN reached out to both el Debek's and Kourani's attorneys, but did not receive a response.