GRAND CANYON, Ariz. — An unknown number of people have died following an early morning fire that engulfed an RV parked near the entrance of the Grand Canyon National Park Monday.

Witnesses at the South Entrance Station called the Grand Canyon Regional Communications Center reporting that a motor home had smoke in the cab. Firefighters arrived on scene just after 7:20 a.m. and were able to extinguish the flames and determined the RV had been occupied at the time of the fire and fatalities had occurred, according to Shannan Marcak, park spokesman.

The National Park Service will be conducting an investigation of the incident, with the assistance of Flagstaff Fire Department and Arizona's Coconino County medical examiner, who was helping to determine the number of fatalities.

Additional information was not available Monday.

Wendy Leonard, Twitter: wendyleonards