A medical helicopter crashed Tuesday amid the hills of central Arkansas, killing three crew members who were trying to reach a person injured in a traffic accident and scattering debris across an area about a quarter-mile wide.

The Air Evac Lifeteam helicopter, a Bell 206 built in 1978, went down near the Scotland community in Van Buren County at about 4 a.m., according to the company and the Federal Aviation Administration.

Pilot Kenneth Robertson, flight nurse Kenneth Meyer, Jr., and flight paramedic Gayla Gregory all were killed, Air Evac spokeswoman Julie Heavrin said. There was no patient aboard the aircraft, Heavrin said.

Van Buren County Coroner Dorothy Branscum said the victims were killed on impact.

"I would say they might've seen it coming, but that was it. The helicopter was just melted and it was just in pieces," Branscum said.

Investigators said autopsies, which were to be performed by the state medical examiner's office, would help determine whether a medical emergency among the crew could have caused the accident. It also was too early to say whether "a mechanical anomaly" caused the helicopter to break up in the air, or if the aircraft struck trees that caused parts to fall off as it went down, National Transportation Safety Board investigator Jennifer Rodi said Tuesday evening.

The helicopter hit the ground about 50 yards from a mobile home with an impact hard enough to reduce the metal fuselage to little more than a flat stack, just a few components sticking higher into the air. A door and some other smaller parts ended up much closer to the home's front entrance.

Deputies flagged numerous pieces of the aircraft in an area about a quarter-mile wide around the impact site, Van Buren County Sheriff Scott Bradley said. Numerous farms and horse barns are in the area and the sheriff noted the low-flying helicopter woke several residents and the crash prompted numerous 911 calls.

"They all said they heard a funny roaring sound, then 'boom,'" Bradley said.

FAA spokesman Lynn Lunsford said there apparently was no distress call before the crash.

Air Evac Lifeteam President and CEO Seth Myers said in a news release the helicopter was equipped with night-vision gear.

"This is a tragic day for us here at Air Evac Lifeteam," Myers said. "These were members of our family and we are devastated at this loss. Our focus at this time is on providing support for the family and friends of these crew members."

Air Evac has experienced several fatal helicopter crashes in recent years, including in 2008 when a crash in an Indiana cornfield killed three people and in 2007 when a three-member crew died in a crash in Colbert County, Ala.

In 2006, an Air Evac helicopter crashed in Gentry in northwest Arkansas, killing a patient being transported and injuring the three-member crew.

Last month, an Air Evac helicopter made a forced landing near Tulsa, Okla., after the aircraft's hydraulics failed. No one was hurt.

Still, Heavrin said Air Evac's crash rate is below the industry average. She said she did not immediately have numbers available, but noted the company had received an operator safety award for the last few years from the Helicopter Association International. She said the award goes to operators with an accident rate half or less of the industry average.

Heavrin noted Air Evac operates 93 bases in 14 states. She said the company logged 58,000 flight hours in 2009.