NEW YORK -- 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 involved in the first stage of launch. Orbital says it still plans to fulfil its contract with NASA to deliver all remaining cargo to the Space Station by the end of 2016.

The engines involved are liquid oxygen and kerosene-fueled AJ26 engines made by Aerojet Rocketdyne. The engines were originally designed and produced during the Soviet era in Russia, though modifications have been made.

On its website, Orbital said each AJ26 engine was sent from the Aerojet Rocketdyne facility in Sacramento, California, to the NASA/Stennis Space Center in Mississippi for hot fire acceptance testing, prior to heading to the Wallops Island, Virginia, launch site.

It will introduce an already-planned upgrade to the Antares propulsion system early in 2016.

Orbital Sciences Corp., based in Dulles, Virginia, says there will be no cost increase for NASA and it doesn't expect costs related to the accident to be material for Orbital in 2015.

Shares of Orbital Sciences rose $1.06, or 4.2 per cent, to $26.18 in morning trading Wednesday.