Investigators looking into the cause of the Orbital Sciences Antares rocket explosion last week believe they have found what went wrong. According to the company's CEO David Thompson, one of the two main engines that helps to launch the rocket failed.

The rocket flew for several seconds after liftoff from the Wallops Island Flight Facility in Virginia before the explosion. The commercial spaceflight contractor was sending several thousand pounds of equipment and supplies to the orbiting International Space Station.

Mission controllers were forced to activate the rocket's self-destruction after it was evident that it would not be able to safely reach the space lab. No injuries were reported in the unmanned rocket explosion.

Following the launch failure, an investigation was held. It became clear that one of the Antares' rocket engines were to blame. The malfunctioning engine did not fire on liftoff, forcing controllers at Orbital Sciences to shut down the operation.

Thompson also added that despite the recent failure, Orbital Sciences does plan to continue its nearly $2 billion contract with NASA to make supply deliveries to the ISS. However, in the future, Thompson said the failed AJ26 engine will no longer be used to launch the rocket.

"We will likely discontinue the use of the AJ26 rocket engines that had been used on the first five Antares launch vehicles unless and until those engines can be conclusively shown to be flight-worthy," he said.

A Russian space program design is reportedly what Orbital Sciences is currently considering to replace the engine in its next rocket. The private company said they will also remove older engines on other rockets that will be used in later resupply missions. The Russian space agency sent a replacement shipment to the ISS soon after the Antares explosion, which helped solidify an association between Orbital Sciences and Russian rocketry.