Russia’s S-400 “Triumf” missile system is touted by many as the most advanced anti-aircraft platform on the planet. When equipped with its longest-range interceptors, the 40N6 missile, the S-400 is reportedly capable of engaging airborne targets as far as 250 miles away. It makes this system of particular interest to China, which is working to shore up its coastal defenses as a result of heightening tensions in the Pacific with the United States and its allies.

China signed a deal with Russia’s state-owned arms manufacturer, ROSTEC, to purchase the S-400 system back in 2015 but didn’t receive the first two platforms until April of last year. Now, reports are emerging that a shipment of those long-range 40N6 missiles destined for Chinese S-400 systems was lost at sea as a result of a storm.

“The contract was signed quite long ago. We were to supply [the 40N6 missiles,] but there was a failure,” said ROSTEC CEO Sergei Chemezov. “The vessel that was transporting those missiles–it was caught in a storm. So they have to liquidate all the missiles that were on the vessel and now we are manufacturing new ones.”