MIDLOTHIAN (June 3, 2010)---A 10-member team has been assembled to investigate the crash of a CareFlite helicopter in a rural area southwest of Dallas, a National Transportation Safety Board official said Thursday.

NTSB air safety investigator Tom Latson said it's too early to say why the helicopter crashed Wednesday during a maintenance right, killing the pilot and mechanic.

No one else was on board.

Latson said the wreckage was discovered in three distinct pieces; the fuselage, the main rotor assembly and the tailboom.

Investigators will interview witnesses and study the craft's structural and electrical components, Latson said Thursday.

The helicopter took off from Grand Prairie, where the nonprofit air transport EMS service is based.

Federal Aviation Administration spokesman Lynn Lunsford said the weather conditions were clear at the time of the crash.

A source told a Dallas TV station it appears the main rotor of the helicopter somehow detached from the aircraft and cut off the tail section, which was found relatively intact.

"The main rotor was separated from the actual crash site by 100 yards," said Dale McCaskill, a spokesman for the Midlothian Fire Dept.

The Helicopter was a Bell 222 model.

CareFlite is a Grand Prairie-based nonprofit EMS service that owns a fleet of nine helicopters and an airplane.

It provides service within a 150-mile radius of the Dallas-Fort Worth area.

This was the fourth crash involving a CareFlite helicopter since 1996 in North Texas, but the first one in which someone died.