Three news sites are reporting that an Antares AJ-26 engine failed Thursday during a test firing at Stennis Space Center. NASASpaceflight.com quoted sources saying the engine “exploded” on the E Complex test stand.

Spaceflightnow.com said the Russian-built rocket engine was damaged during the “test mishap” but there were “no injuries.”

The engine was slated to be one of two used to launch Orbital Sciences Corp.’s resupply flight to the International Space Station next year.

Spacenews.com is the third site reporting the test failure.