Delwin and Tamara Chapman were in Las Vegas to renew their wedding vows after 25 years of marriage when a luxury helicopter tour of the twinkling Las Vegas Strip and the iconic Hoover Dam.

The sunset tour ended in a smoky crash Wednesday night, killing the Chapmans, a 31-year-old pilot and two other passengers in an accident that scattered helicopter debris across the River Mountains bordering Lake Mead.

Clark County Coroner Michael Murphy said the bodies were not easily recognizable and identifying the victims would likely involve the use of DNA, fingerprint and dental records.

It is unclear what might have triggered the Nevada crash. The weather was mostly clear Wednesday near Lake Mead with a low temperature around 29 and winds around 5 mph. Investigators expect to be on the scene three to five days, said Mark Rosekind, with the National Transportation Safety Board.

He said the helicopter crashed near the bottom of a V-shaped canyon about 150 feet deep. Investigators had to climb ladders into the canyon to survey the scene.

Investigators have identified both tail rotor blades and parts of the engine, Rosekind said at a news conference Thursday night. There is evidence the main rotor blades remained attached to the rotor hub of the ill-fated aircraft, he said.

The crash was the latest involving tour helicopters across the country in recent years and comes amid concerns about the safety of the air tour industry. From 1994 through 2008, there were 75 commercial helicopter accidents in the United States, excluding air ambulances, resulting in 88 fatalities.

A helicopter that was using cables to install a seven-story Christmas tree in central Auckland, New Zealand, crashed down to the ground. The pilot, Greg Gribble, escaped virtually unharmed with only minor injuries, while no one else was hurt, despite the fact that workers were very close by under the helicopter when the incident occurred.

While the circumstances of the accident are not yet clear, it appears that the helicopter’s main rotor blades may have got caught in the cables. The family company that owns the chopper, Heli-Sika Helicopters, said: “Thanks everyone for their support and concerns, we are very lucky that Greg is all okay! Apart from being in Shock and having a very sore head!”

Their helicopter crashed in foul weather during a mission to airlift troops on a patrol mission to combat the forest encroachment and illegal logging in the national park.

The seven soldiers who were stranded in the park had walked to the crash site after the helicopter, unable to pick them up, eventually crashed. The helicopter wreckage was completely damaged and all five crew members and passengers were killed.

A forest protection unit from Kaeng Krachan National Park would be dispatched by helicopter to the nearest possible area and would travel by foot to the site to recover the bodies. The mission was expected to take at least one day.

The agencies said that the military helicopter crashed in daylight Tuesday attempting an emergency landing after engine failure in the province of Stavropol. A co-pilot was injured, the reports said.

The military routinely grounds aircraft after disasters.

The Mi-28 is nicknamed Night Hunter because of its sophisticated radar equipment that allows night missions, and is roughly analogous to the U.S. Boeing AH-64 Apache.

Attorneys hired by National Bank of Indianapolis filed the lawsuit in Marion Superior Court last week on behalf of Pearson’s two children, Gabrielle, 8, and Garrett, 10.

“These helicopter crashes have real human life consequences,” said Gary Robb, a Kansas City, Mo., attorney representing the plaintiffs. “I’m going to make sure these children do not have any kind of financial hardship over the death of their mother.”

Jefferson County Justice of the Peace identified three victims, whose bodies were recovered the day of the accident, as: the pilot, 43-year-old Joseph Laugelle Jr. of Quincy, Mass.; 23-year-old James Cody Smalts of Huntsville; and 51-year-old John Larry Conn of Katy.

The body of 26-year-old Jacob Matt of Jennings, La., was discovered Dec. 15 by volunteers patrolling a beach at the McFaddin National Wildlife Refuge.

The Sikorsky S-76C, carrying a pilot, co-pilot and seven workers bound for a Shell Oil platform in the Gulf of Mexico, crashed about 2:10 p.m. Sunday in a marshy area of western Terrebonne Parish near Bayou Penchant, authorities said.

Boudreaux, who lived with his mother in Ama, was one of five men working for New Iberia-based Dynamic Industries who were headed to the platform aboard the helicopter. Three of his co-workers, Ezequiel Cantu, 35, Andrew Moricio, 30, both of Morgan City and Randy Tarpley, 53, of Jonesville, died in the crash.

Two other passengers killed, Jorey Rivero, 35, of Bridge City and Charles W. Nelson, 24, of Pensacola, Fla., worked for MMR Offshore Services, headquartered in Baton Rouge, officials said.

Pilot Thomas Ballenger, 63, of Eufaula, Ala., and co-pilot Vyral Martin, 46, of Hurst, Texas, were also killed.

According to deputy air force spokesman, the plan crashed when it was landing at the station.

A thorough investigation would be done to see whether heavy rain and wind at the time were the cause of the crash.