MARTINSBURG, W., Virginia (Reuters) - A World War II-era plane crashed in a fireball on Saturday at a West Virginia air show, officials said, a day after another vintage plane crashed at a show in Nevada, killing nine people and injuring more than 50 others.

There was no immediate word on any casualties in West Virginia, officials said.

The T-28 aircraft crashed at about 2:40 p.m. during an acrobatic demonstration at the 2011 Thunder Over the Blue Ridge Open House & Air Show in Martinsburg, said a spokesman for the West Virginia Air National Guard.

According to Federal Aviation Administration spokesman Jim Peters, the plane was part of a formation of six T-28s.

The plane, which crashed onto a runway, was registered to John Mangan of Concord, North Carolina.

"At this point we don't know the extent of injuries or the damage to the aircraft or whether or not anyone was injured on the ground," Peters said."

Witnesses at the air show reported a large fireball. West Virginia Senate Majority leader John Unger, whose district includes Martinsburg, was at the air show with his family.

"All of a sudden I heard my wife say, 'Oh my goodness' and then I heard a boom, like clap, and I looked over and there was a ball of fire," Unger said. "When I saw it, it had already hit the ground and it was sliding in a big flame."

Another witness said he was watching the T-28 perform a mid-air crisscrossing stunt with a similar plane.

"After crossing each other, the plane to my right lowered closer to the ground and from what I saw was at almost a sideways angle and rolled onto its side," said Morgan McAckern, a college student.

"It looked very much like the tip of one of the wings clipped the ground and dragged before exploding," he said.

Officials with the Air National Guard said they would hold a press briefing later on Saturday.

The T-28 plane was used for training by the Navy and Air Force between 1950 and 1984.

Another historic plane, a P-51 Mustang, crashed on Friday near the grandstand in a Reno, Nevada air race, killing nine people and injuring more than 50 others.

Among those killed was the pilot, Jimmy Leeward. The National Transportation Safety Board and Federal Aviation Administration are investigating.

(Additional reporting by Barbara Goldberg, editing by Ellen Wulfhorst)

mochila insert follows