A dispatcher for the Hualapai Department of Emergency Services told Phoenix television station KNXV that the helicopter was on a tour of the canyon, one of the top U.S. tourist destinations and more than a mile (1.6 km) deep, when it went down.
He said three people were killed and four had unknown injuries, and that authorities were possibly looking for one or two more people, the station reported.
The Hualapai Department of Emergency Services directed calls to police, who did not respond immediately to a request for comment.
Allen Kenitzer, a spokesman for the Federal Aviation Administration, said in an email that the helicopter, an Eurocopter EC130 from Airbus, “crashed under unknown circumstances in the Grand Canyon” and suffered substantial damage.
“Local authorities say that at least seven people were on board the helicopter.
“The Federal Aviation Administration and the National Transportation Safety Board will investigate,” Kenitzer said.