Followers of Yemen's al-Houthi Shi'ite group
Followers of Yemen's al-Houthi Shi'ite groupReuters

Yemeni authorities working with the United States Navy intercepted a ship carrying a substantial cache of illegal arms that U.S. officials suspect were being smuggled from Iran. 

The arms, intercepted aboard the ship in Yemeni territorial waters in the Arabian Sea last Wednesday, included surface-to-air missiles, potent explosives and rocket-propelled grenades, a U.S. official and Yemen's government announced Monday.

The crew of the USS Farragut, a Naval destroyer, was working with Yemeni authorities when they spotted the vessel, said an official in the Obama administration, speaking on the condition of anonymity.

The ship had several flags onboard, but no reliable documentation showing where it came from, the official added Monday, five days after the event occurred.

Yemeni coast guard officers boarded the ship and "found a large cache of illegal arms," according to the Yemeni embassy's statement.

The firepower included anti-aircraft missiles, C4 military-grade explosive, ammunition and bomb-making equipment such as circuits, remote triggers and various handheld explosives, the statement said.

The intercepted shipment was believed to have been from Iran and destined for insurgents, like Houthis.

"This demonstrates the ever pernicious Iranian meddling in other countries in the region," said the US official.

There were eight Yemeni crewmembers aboard the vessel.

An investigation is underway to reveal the source and destination of the weapons.