Six people who were on board a small twin-engine plane that crashed in Arizona on Wednesday in the remote area of the Superstition Mountains appear to have been killed, authorities said. Three of the people presumed dead were believed to be children.

Pinal County Sheriff Paul Babeu told reporters that the other people who were believed to be on board the plane were a pilot, a mechanic and another adult.

He said the children were being flown to Arizona for the Thanksgiving holiday. The plane refueled shortly before it crashed and there were no immediate signs of survivors among the six presumed dead. 

The crash started a wildfire, authorities told Reuters.

Babeu said helicopter dropped 10 search and rescue workers into the area near the crash to look for survivors.

At this point, we can't confirm there would be survivors, Babeu said. Our hope is that there would be, but it does not look promising.

Pinal County Sheriff's Office spokesman Elias Johnson has said if rescuers were to approach the crash site by foot it would take about six-hours. He said the accident happened in a steep, cliff-like terrain that is near a remote summit in the Superstition Mountains, 45 miles east of Phoenix.

Preliminary reports are that the plane was a Rockwell AC69 twin engine aircraft.

Allen Kenitzer, a spokesman for the Federal Aviation Administration, told Reuters that the small plane took off from Falcon Field, in the Phoenix valley. The plane was registered to Safford, Arizona-based Ponderosa Aviation, an air charter firm.

What we understand is that this aircraft flew from Safford to Falcon Field in Mesa (near Phoenix) to pick up children for Thanksgiving, to go back to Safford, so it's heartbreaking if that's the case, Babeu said.

The company's Web site shows that it has eight full-time pilots and has been in operation since 1974.