Washington — Four foreign nationals who were allegedly transporting Iranian-made weapons on a vessel that two U.S. Navy SEALs drowned trying to board have been brought to the U.S. to face criminal charges, making their first appearance in court on Thursday.

The defendants — Muhammad Pahlawan, Mohammad Mazhar, Ghufran Ullah and Izhar Muhammad — were taken into custody when a U.S. Navy ship intercepted their small boat in the Arabian Sea on Jan. 11. The vessel, or dhow, was allegedly destined for Yemen.

A team of SEALs from the USS Lewis Puller and a U.S. Coast Guard response team boarded the unflagged boat in a nighttime raid and seized "what is believed to be Iranian-made advanced conventional weaponry," according to charging documents unsealed Thursday. A total of 14 crew members were on board. In addition to the four co-defendants, eight of the remaining 10 witnesses are also in U.S. custody.

Prosecutors wrote that the vessel was transporting "propulsion and guidance components" for medium-range ballistic missiles and anti-ship cruise missiles, as well as a warhead. The weapons were likely intended for Houthi rebels in Yemen, who have attacked dozens of commercial and military vessels in recent months, according to investigators. 

The Navy SEALs' deaths

Two of the SEALs — Special Warfare Operators Christopher Chambers and Nathan Ingram — were lost at sea during the mission. Defense officials told CBS News at the time that they fell overboard in rough seas while trying to board the dhow. After a 10-day search, the military declared the two SEALs deceased.

None of the defendants have been charged directly with the SEALs' deaths. According to prosecutors, Pakistani identification cards matching their names were found onboard their boat. 

The seizure was the first time the U.S. military intercepted weapons from Iran destined for the Houthis since the rebel group ramped up their attacks on commercial shipping and international warships in the Red Sea in November 2023.

According to court papers, all of the crewmembers denied smuggling the weapons once they were in custody, though a few admitted to being drug smugglers. Other crew members identified Pahlawan as the leader of the group. He said he had been in Iran for two years and that the ship left Iran six days before it was intercepted by the Navy. 

Pahlawan said the ship's Iranian owner gave him a satellite phone to communicate while at sea. Investigators said the phone received calls from a number associated with a member of Iran's Islamic Revolutionary Guard Corps, an elite branch of the country's military.

U.S. investigators said that the ship originated in Iran on a route that included a stop in Somalia. The path was "consistent with other weapons smuggling operations," the government said. 

The FBI and NCIS twice interviewed Pahlawan. He denied being the captain of the boat or knowing about the weaponry, but admitted to being the senior sailor onboard. 

"Two crew members indicated that Pahlawan told crewmembers not to stop the [boat] while the Navy was approaching the dhow," according to charging documents. "At least one crewmember said that [Pahlawan] tried to make the dhow go faster when the Navy was approaching. Multiple crewmembers said it was another crewmember, and not [Pahlawan], who stopped the boat." 

The other three defendants also denied knowing about the weapons on the ship. They are charged with providing materially false information to investigators. 

Pahlawan faces that charge, plus one count of intentionally and unlawfully transporting explosive material on a ship, knowing it would be used to cause harm. 

"Due to the publicity of the war in Israel and the Houthis' attacks on vessels in the Red Sea as a means of protesting the United States' support of Israel and as a means of supporting Hamas and Palestine … there is probable cause to believe that Pahlawan knew that the weaponry would be used by the Houthis against American and/or Israeli targets or interests," prosecutors alleged Thursday. 

He faces a maximum of 20 years in prison if convicted.

The four defendants and eight of the witnesses who were aboard the small boat made their initial appearances in federal court in Virginia on Thursday, the Justice Department said. 

"The Justice Department extends our deepest condolences to the families and loved ones of the two Navy SEALs who lost their lives on January 11th while conducting an operation in the Arabian Sea," Attorney General Merrick Garland said in a statement. "The charges resulting from that interdiction make clear that the Justice Department will use every legal authority to hold accountable those who facilitate the flow of weapons from Iran to Houthi rebel forces, Hamas, and other groups that endanger the security of the United States and our allies."

Houthi rebels have now attacked or threatened ships in the Red Sea at least 60 times since November 2023, according to a defense official. The strikes are in response to ongoing war between Israel and Hamas in Gaza, which began after Hamas' attacks across Israel on Oct. 7. 

The U.S. military has since conducted roughly 30 defensive strikes targeting the Houthis, according to the Pentagon.

Robert Legare

Robert Legare is a CBS News multiplatform reporter and producer covering the Justice Department, federal courts and investigations. He was previously an associate producer for the "CBS Evening News with Norah O'Donnell."