"Three passengers are confirmed deceased and there are four level 1 trauma patients at the scene", Bradley said.
A helicopter, a Eurocopter EC130, crashed under unknown circumstances, FAA spokesman Allen Kenitzer wrote in an email. Federal authorities are expected to investigate the incident.
The helicopter was operated by Papillon Airways, an aerial sightseeing company that gives tours of the Grand Canyon and other locations, Bradley said.
Photos of the crash scene showed flames and dark smoke rising from rocky terrain. Papillion Airways is based in the Las Vegas area.
He earlier told USA media that the local terrain had hampered rescue efforts overnight.
National Weather Service meteorologists in Flagstaff and Phoenix said wind conditions were an estimated 10 miles per hour with gusts of 20 miles per hour around the time of the crash. He said one of them "was pretty much burned all over".
According to reports, the place was reportedly carrying six passengers and a pilot. "We had to learn how to market Las Vegas", he said.
The company's website said it flies roughly 600,000 passengers a year around the Grand Canyon and on other tours.