LAS VEGAS (AP) — Recovery and investigative teams are heading to a remote site near Lake Mead where a helicopter slammed into a mountainside, killing the pilot and the four passengers who were on a tour of the Las Vegas Strip and Hoover Dam, federal authorities said.

The aircraft operated by Sundance Helicopters crashed just before 5 p.m. Wednesday, said National Park Service spokesman Andrew Munoz.

Numerous witnesses heard the crash and reported seeing smoke about 4 miles west of the lake’s edge, Munoz said.

He said a Las Vegas police search and rescue team reached the scene by helicopter and confirmed that all five people on board were dead.

The remote crash site in the River Mountains surrounding Lake Mead, about 30 miles from the Las Vegas Strip, is not accessible by road, which slowed down the initial rescue and later prompted officials to delay any recovery and investigation until early Thursday morning.

The National Transportation Safety Board said it was launching a 12-member team to investigate the crash.

A park ranger rode in a 4-wheel-drive truck to the crash site late Wednesday to protect the bodies and debris until the investigation resumes, Munoz said.

Authorities did not release any information about the identities of the victims.

A spokesman at Sundance Helicopters told The Associated Press that the helicopter had been giving a local tour when it suddenly went missing.