Unmanned NASA rocket explodes after launch

An Orbital Sciences Corporation unmanned spacecraft exploded Tuesday six seconds after launch on a resupply mission to the International Space Station, NASA said.

"The Antares rocket suffered an accident shortly after lift-off," NASA mission control in Houston said.

Fires were seen burning at the coastal launch pad after the Antares rocket blasted off at sunset from Wallops Island, Virginia at 6:22 pm (2222 GMT).

It was unclear what caused the explosion.

"At this point it appears that the damage is limited to the facility," a commentator on NASA television said.

"There is no indication that there are personnel in danger, although we do have significant property damage and significant vehicle damage."

NASA mission control said the accident occurred just after Orbital's unmanned Cygnus cargo ship blasted off toward ISS carrying 5,000 pounds (2,200 kilograms) of supplies for the six astronauts living at the research outpost.

It was the first nighttime launch of an Antares rocket, said Orbital.

The mission, known as CRS-3, was to be Orbital's fourth trip to the ISS, including an initial demonstration.