LITTLEFIELD, Ariz. -- Two people were killed in a plane crash in Mohave County Sunday evening.The pilot, 19-year-old Daulton Rey Whatcott, was traveling with his younger brother, 16-year-old Jaxon McKee Whatcott. Both were from Clinton City, Utah. No other occupants were on board. Mohave County sheriff's deputies responded to the crash just south of Interstate 15 in the Arizona Strip at about 6:30 p.m. A spokesman with the Federal Aviation Administration said that the plane went down "under unknown circumstances" in Littlefield and was on fire.Mohave County Sheriff's Office spokeswoman Trish Carter said the 1969 Cessna 172k fixed-wing single-engine was traveling from Bountiful, Utah, en route to Mesquite, Nevada.Carter said the remains of both victims have been recovered.The cause of the crash is unknown at this time. The National Transportation Safety Board and the FAA are investigating.It was the second plane to go down in Arizona on Sunday. Four people died in a crash near Sedona at around 4 p.m. The crash sparked a wildfire.