Los Angeles, Dec 8 (IANS): A helicopter crashed near Las Vegas Wednesday evening killing four passengers on board and the pilot, an official said.

The accident occurred around 5 p.m. when the chopper, operated by Sundance Helicopters, was taking passengers on a tour over Hoover Dam and went down outside of the Lake Mead National Recreation Area, east of Las Vegas, authorities quoted by local media said.

Several witnesses reported smoke and what appeared to be wreckage in the area, reported Xinhua citing a TV report.

Police spokesperson Bill Cassell said rescuers were trying to reach the isolated area of the crash, but later the rescue mission turned to a recovery effort after it was discovered that the five on board were killed.

The cause of the accident was still unknown.

The helicopter was an Aerospatiale AS350, which can hold up to six passengers and are often used for air tours.

Founded in 1985, Sundance Helicopters operates the largest and most experienced helicopter company in Las Vegas, featuring daily Grand Canyon Helicopter Tours. The company says on its website that it carries "more than 160,000 customers safely each year".

In September 2003, a Sundance Grand Canyon tour helicopter crashed, killing all seven people on board, including at least four foreign tourists.