MIDLOTHIAN, Texas (AP) - A National Transportation Safety Board official says a team of 10 has been assembled to investigate the air medical helicopter crash that killed two on board.

NTSB air safety investigator Tom Latson says it's too early to say why a CareFlite helicopter went down in a rural area southwest of Dallas during a maintenance run Wednesday. The pilot and mechanic were killed. No patients were on board.

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

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

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

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