According to Papillion Airway's website, the carrier flies roughly 600,000 passengers a year on tours of the Grand Canyon and other areas.
Hualapai Nation Police Chief Francis Bradley said the crash happened Saturday night near Quartermaster Canyon on the Hualapai Nation about 60 miles west of Peach Springs, Ariz. There were a total of seven people on board, including the pilot.
A Eurocopter EC130 crashed in "unknown circumstances" at around 5.30pm, Allen Kenitzer, a spokesman for the FAA, told ABC News.
Bradley said four people remain at the scene and have been classified as "level one trauma patients". The other four were critically injured, and were still being treated at the scene.
Crews will work Sunday to retrieve the bodies of those who died in the crash, Bradley said, but weather conditions were hampering efforts.
Images of the crash site online showed flames and black smoke shooting from a ravine.
"This is not just the fact that a helicopter crashed, this is a human tragedy".
The Arizona Department of Public Safety said the organization was assisting the National Park Service with the crash.
Federal authorities are expected to investigate the incident.
NTSB investigators determined the probable cause of the 2001 crash was pilot error.