The tourist group was celebrating their friend's 30th birthday.
Grand Canyon
Credit: Shahrzad Gholami/EyeEm/Getty Images

A helicopter crash in the Grand Canyon, in Arizona, killed three people and severely injured four others on Saturday. All of the victims were British tourists, except for the pilot.

The tour helicopter crashed inside a gully on Hualapai Nation's land near Quartermaster Canyon.

It remains unclear what caused the crash, but severe winds gusting up to 50 miles per hour hampered the rescue efforts, which lasted for hours into the night, BBC reported.

The three people who died — Becky Dobson, 27, Stuart Hill, 30 and his brother Jason Hill, 32 — were celebrating Stuart's 30th birthday, according to the same BBC report.

Witnesses described billowing smoke and badly burned victims emerging from the helicopter, Associated Press reported.

“It's just horrible,” witness Teddy Fujimoto told AP. “And those victims — she was so badly burned. It's unimaginable, the pain.”

Papillon, the company that ran the helicopter tours, described itself on its website as “the world's largest aerial sightseeing company.” The tour operator leads the tours for some 600,000 visitors annually.

Helicopter tours of the Grand Canyon have long been a popular way to see the national park. This incident was not the first deadly crash: The same tour operator suffered a deadly crash in 2001, killing the pilot and five passengers, according to records from the National Transportation Safety Board (NTSB).