An aging North Korean freighter similar to the one impounded by Panama for carrying concealed Cuban military equipment made the same voyage last year without attracting suspicion, passing through the Panama Canal and calling at the same two Cuban ports, an international maritime traffic monitor said Wednesday.
The monitor, IHS Fairplay, said that both vessels -- the 390-foot Oun Chong Nyon Ho, which made the voyage last year, and the 450-foot Chong Chon Gang -- normally worked much closer to North Korea, making their trans-Pacific trips to Cuba even more unusual.
"They don't normally make these ocean passages," Richard Hurley, a senior maritime data specialist at IHT Fairplay, said in a telephone interview from the group's London offices. "It's intriguing to see two fairly small ships making the same pattern."
He said a new review of IHS Fairplay tracking data showed that the two freighters were among only five North Korean cargo vessels that have traversed the Panama Canal since 2010, underscoring the rarity of North Korean shipping in the area.
The revelation of what Mr. Hurley called a "mirror image" voyage in 2012 by the Oun Chong Nyon Ho added a new twist to the intrigue surrounding the impounded ship, which has been docked at the port of Manzanillo, Panama, since Sunday. Its captain and crew were detained at a naval base after they violently resisted a boarding party of Panamanian marines acting on a tip that the ship was carrying contraband.
The marines discovered a load of Russian-built military equipment owned by Cuba, including antiquated Soviet-era radar gear, hidden among more than 200,000 sacks of Cuban brown sugar. After two days of silence, Cuba acknowledged the cargo Tuesday night, describing it as "obsolete defensive weapons" sent to North Korea to be refurbished.
Angry Panamanian officials have protested the attempt to ship the clandestine cargo through the canal as a violation of United Nations Security Council sanctions on North Korea, which has yet to comment publicly on the entire episode. The shipment also threatens to derail recent efforts by the Cuban government to ease its prolonged estrangement from the United States, where some lawmakers are already calling for retribution.
At the United Nations on Wednesday, a spokesman for Secretary General Ban Ki-moon said he was aware of the impounded ship's reported cargo but that it was the responsibility of the Security Council's sanctions committee to determine violations.
At the same time, the spokesman, Martin Nesirky, said if the vessel from North Korea was found to have been carrying arms or related material from a purchase or sale, "that would indeed be a breach of the U.N. sanctions regime relating to that country."
The 35 detained North Koreans, including the captain, who had sought to commit suicide after his ship was impounded, were receiving unspecified medical attention, the Panama prosecutor's office said Tuesday night. In a possible indication that they may face criminal charges, the office said they would be assisted by Panamanian lawyers and interpreters in interrogations.
It was not known what cargo the Oun Chong Nyon Ho might have carried to or from Cuba in 2012. The tracking data from IHS Fairplay showed that it made the same Cuban port calls as its impounded sister vessel, stopping first in Havana for a few days in May 2012, then visiting Puerto Padre, a major sugar export point, for five days, then returning to Havana for a stopover of about three weeks, before heading home through the Panama Canal.
Mr. Hurley said he could only presume that the Oun Chong Nyon Ho picked up a load of sugar at Puerto Padre, but that the voyages of both freighters were still steeped in mystery. Sugar is a major Cuban export, but North Korea is not a frequent customer. "Perhaps they need to fill up the Dear Leader's sugar bowl once a year," he said, referring to Kim Jong-un, the current leader of North Korea.
Karla Zabludovsky contributed reporting from Mexico City.
This article originally appeared in The New York Times.