National Transportation Safety Board investigators were on their way to the scene, about 20 miles north of this Texas Panhandle town.

``We don't know whether he hit power lines or had a mechanical failure,'' said NTSB spokesman Doug Wigington. ``We are also looking to see if weather might be a possible cause.''

The Life Star helicopter left Northwest Texas Healthcare System in Amarillo to pick up the girl in Boise City, Okla., about 100 miles to the north, and was returning at the time of the crash.

The craft, which was leased to the small Amarillo hospital, had landed about 15 miles south of Boise City because of fog and was met by an ambulance carrying baby Kathy Esparza, authorities said.

After the child was put aboard, the helicopter took off in fog at 6:05 a.m., and the crew was not heard from again, said Department of Public Safety Sgt. James R. Woodrum. When the fog lifted nearly five hours later, the wreckage was discovered less than a mile away.

The transfer and the crash occurred near the community of Coldwater, Texas, three miles south of the Oklahoma state line. The helicopter was following power lines along a roadway, officials said.

``It looks like they impacted on their nose and nobody knows exactly why. It looks like it either exploded or started burning immediately on impact, and then it caught the grass on fire,'' Woodrums said.

The debris was scattered over an area about 400 feet by 100 feet.

Kathy's mother, who was driving to the hospital, didn't learn of the crash until she arrived in Amarillo, said Moody Chisholm, chief executive officer of Northwest Texas Healthcare System. Parents typically do not ride in the helicopter.

The helicopter had no history of accident or safety problems, said John Clabes, a Federal Aviation Administration spokesman. The craft was leased to the hospital by TEMSCO Helicopters Inc. of Ketchikan, Alaska.

Flags were at half-staff at the Amarillo hospital on Friday. Helicopter pilots and hospital staff members gathered in the hallways, hugging and crying.

``We have absolutely saved hundreds and hundreds of lives with this helicopter,'' Chisholm said. ``We are all in a lot of pain that we have lost this crew and patient. If we can get past this, it still is a service that is needed out here.''

He said Lauren Stone, a 30-year old flight nurse, and Terry Griffith, a 35 year-old flight paramedic, were killed in the crash. The identity of the pilot wasn't released.

The crash was the second fatal medical helicopter accident in Texas within a year. Three crew members died in July when a helicopter based at Hermann Hospital in Houston crashed outside the city.