Substantiating suspicions right after the spectacular fireball that destroyed a rocket carrying cargo to the International Space Station, the manufacturer of the rocket said Wednesday that the fault most likely lay in Soviet-era rocket engines that powered the first stage.

On Oct. 28, the Antares rocket, loaded with about 5,000 pounds of supplies, equipment and experiments, exploded about 15 seconds after rising off a launching pad at Wallops Island, Va. Nobody was injured.

The Orbital Sciences Corporation of Dulles, Va., which has a $1.9 billion contract with NASA to take cargo to the space station, said Wednesday that its preliminary analysis pointed to a failure of a turbopump, which pushes high-pressure fluid into the engine’s combustion chamber. The first stage of the rocket uses two AJ26 engines, which are refurbished from ones originally built in the 1970s for a Soviet moon mission.