(CNN) -- A helicopter crashed Saturday north of Phoenix with preliminary reports of no survivors, authorities said.

It was not known how many people were aboard.

Witnesses along Interstate 17 reported flames and black smoke about 70 miles north of Phoenix about 11:50 a.m., said Dwight D'Evelyn, spokesman for the Yavapai County Sheriff's Office.

The privately owned UH-1V helicopter was destroyed, said Federal Aviation Administration spokesman Ian Gregor. He said there was no early indication of the circumstances of the crash.

The helicopter is registered in the Phoenix area, D'Evelyn said.