Orbital Sciences says it will likely stop using the type of engines that were employed when its unmanned Antares commercial supply rocket bound for the International Space Station exploded moments after liftoff last week.

The company says its investigation of the crash is continuing, but preliminary results point to a failure in one of its two main engines. Orbital says it still plans to fulfill its contract with NASA to deliver all remaining cargo to the Space Station by the end of 2016.

Orbital Sciences Corp., based in Dulles, Virginia, says there will be no cost increase for NASA. It will introduce an already-planned upgrade to the Antares propulsion system early in 2016.

Orbital doesn't expect costs related to the accident to be material in 2015.