SEDONA: Two small planes went down in separate crashes in Arizona, leaving six people dead, authorities said.

The Yavapai County Sheriff's Office said four died when a plane crashed near Sedona. Later, authorities said a small plane crashed near the Utah border, killing two people.

The US Federal Aviation Administration said the plane went down “under unknown circumstances” and was on fire. There was no word Sunday on the identities of any of the dead or the causes of the crashes. The FAA and the National Transportation Safety Board will investigate both crashes.