(AP) Federal investigators sifting through the wreckage of a business jet that crashed in North Carolina and killed retired NASCAR driver Greg Biffle, his family, and three others are trying to figure out who was flying the plane and what caused it to return to the airport soon after takeoff. The Cessna C550 erupted into a large fire when it hit the ground Thursday, killing all seven on board. It had departed Statesville Regional Airport, about 45 miles (72 kilometers) north of Charlotte, but crashed less than 10 minutes later while trying to return and land, authorities said.