Three people were found shot to death in a vehicle on the Navajo Nation, the FBI said Monday.

FBI special agent Bill Elwell said the "execution-style" murders occurred along a dirt road just east of Shiprock. A motive was not immediately known.

The victims were two unidentified men and a woman, Vickie Benally, 26, of nearby Farmington.

Elwell said it appeared all three were shot while inside the parked vehicle, which was struck by several bullets. It was unclear how many assailants were involved.

The FBI was seeking clues to Benally's whereabouts on Sunday night as part of an investigation, Elwell said, but he would not elaborate.

Shiprock is on the Navajo Nation in the Four Corners region, where New Mexico, Utah, Colorado and Arizona meet.