Federal investigators in Oregon will work to determine why a helicopter on a test flight collided with another chopper flown by a young instructor and her student, killing all three people aboard both aircraft.

The National Transportation Safety Board said Friday morning that its team was on its way to examine the wreckage near the airport in McMinnville, about an hour's drive southwest of Portland.

The town lies in the broad, flat Willamette Valley near the foothills of the Coast Range, in the heart of Oregon's wine country.