The crash of a single-engine plane that killed a Salt Lake couple and their son and his family likely was caused by a sudden shift in the wind, a federal investigator says.

Norm Wiemeyer of the National Transportation Safety Board said Friday his preliminary findings indicate no failure in the plane's structure or engine contributed to Tuesday's crash.The plane was intact and the engine was running when it nosedived into a dirt road near the Coronado Airport, he said.

Killed in the crash were Wayne Brown, 60, former dean of the University of Utah College of Engineering, and his wife, Joyce, 58, of Salt Lake City. Also killed were their son Gary Brown, 31, his wife, Melissa, 26, and their daughter, Lindsey, 2, of Albuquerque.

Authorities said the family had visited Carlsbad Caverns earlier in the day and were returning to Albuquerque when they tried to land at the unmonitored airport.

The pilot, apparently Wayne Brown, was making his second landing attempt when witnesses said the plane was hit by a gust of wind, tipped and plowed into the ground.

Wiemeyer said evidence suggests wind shear caused or contributed to the crash.