Engine failure was the cause of the explosion of an unmanned rocket shortly after it lifted off from a launch pad in Wallops Island, Virginia, last month, according to the company behind it.

Orbital Sciences Corp. said in a news release Wednesday that an internal investigation has reviewed both telemetry and video data as well as a "substantial" amount of the debris from the failed Oct. 28 Antares rocket launch.

"Preliminary evidence and analysis conducted to date points to a probable turbopump-related failure in one of the two Aerojet Rocketdyne AJ26 stage one main engines," Orbital added in the news release. "As a result, the use of these engines for the Antares vehicle likely will be discontinued."

The company says it still plans to fulfill 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.

The exploded rocket cost the company at least $200 million in lost equipment and supplies, Agence France-Presse reported, adding that the blast was the first "catastrophic failure" since private companies started supplying the International Space Station four years ago.

See the full story in the press release from Orbital Sciences Corp.

The Associated Press contributed to this report.