A Kansas couple celebrating their 25th wedding anniversary were among five people who died in the crash of a tour helicopter in a remote canyon outside Las Vegas.

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.