North Korea’s latest missiles are strikingly similar to designs that were once up for sale after the collapse of the Soviet Union, according to documents reviewed by The Washington Post. A North Korean missile launched in June 2016 appears to use “the same engine and many design features” as a former Soviet Union missile that was put up for sale in 1992, the Post reports. After the sale fell through, scientists from the Russian missile facility that produced the weapon were arrested attempting to fly to North Korea in 1993. U.S., Russian, and South Korean officials reportedly believe that some scientists reached North Korea. Weapons experts have previously speculated that North Korea’s recent, rapid advances in missile technology may have drawn on Soviet designs.