SMITHSBURG - A helicopter crashed onto Interstate 70 on South Mountain and burst into flames, killing three employees of a Frederick, Md., flight instruction company and a passenger, the company said Friday.

The aircraft was engulfed when firefighters arrived at the scene minutes after receiving a call at 10:30 p.m. Thursday, said Washington County emergency services director Kevin Lewis. No vehicles on the highway were hit when the helicopter smashed into the eastbound lanes of Interstate 70. All four aboard the helicopter were killed, though there were no injuries on the ground.

Three people who worked for Advanced Helicopter Concepts in Frederick and a passenger were killed in the crash, one of its instructors, Gary Smith, said Friday morning. He said the company had suffered a “huge loss.”

“We thank everyone for their support and understanding during this difficult time,” he said, declining to release further details. The company trains pilots, takes photographers on aerial tours and fixes and sells helicopters, according to its Web site.

Visibility was somewhat limited by fog at the time of the crash, but it wasn’t clear if weather played a role, Lewis said. Storms had passed through the area earlier in the night.

Lewis said a witness saw the craft flying low when a bright arc of electricity flashed in the air, apparently caused by the helicopter striking a power line. It wasn’t clear if the craft was already on its way down when it hit the lines.

“The witness basically saw a large arc at which point the helicopter crashed onto the interstate,” Lewis said. Before seeing the arc, the witness thought the helicopter might have been trying to land along the roadway.

Troopers temporarily shut down lanes in both directions at the crash site near Smithsburg, which is about 10 miles east of Hagerstown, and Lewis said there were downed power lines in the interstate. The highway was reopened early Friday.

Wreckage could be seen just off the shoulder of the three eastbound lanes. A blade jutted out from twisted metal. The wreckage is almost directly beneath a set of power lines.

Federal Aviation Administration records list the owner of the four-seat Robinson R44 helicopter as Marsan Aviation Inc., of Wilmington, Del. Telephone messages weren’t immediately returned early Friday by an attorney for Marsan listed in FAA records.

Maryland State police, who are in charge of the investigation, declined to release the victims’ names until family members were notified. Investigators from the National Transportation Safety Board and the FAA were also at the scene west of the Washington County-Frederick County line, on the western slope of South Mountain.

Maryland State police spokesman Greg Shipley said the bodies were being taken to the state medical examiner in Baltimore. Any information about the owner of the aircraft and the cause of the crash will come from NTSB, which will conduct a briefing Friday morning at the Hagerstown Regional Airport.

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