Five people, a pilot and four passengers, are trapped on board a private tour company airplane that crashed in Denali National Park Saturday evening, according to Lt. Col. Candis Olmstead of the Alaska National Guard.

The condition of the people on the plane is unknown, but a rescue mission is currently underway.

The Alaska Rescue Coordination Center received a request for assistance in response to the crash around 6 p.m., and have been tasked with the rescue mission.

Katherine Belcher, a spokesperson for the National Park Service, said the plane left Talkeetna at 5:06 p.m. for a one hour tour with weather described as cloudy. Talkeetna-based flightseeing company K2 Aviation was operating the plane, said to be a DeHavilland DHC-2 Beaver.

"The plane is reportedly equipped with an emergency survival kit including sleeping bags, a stove and pot to boil water, food supplies, first aid kit and other items," wrote Belcher.

Officials say the plane crashed onto a feature unofficially known as Thunder Mountain at around 10,920 feet elevation. The crash site is said to be on a knife-edge, extremely steep and "more of a ridge than a mountain, stretching roughly a mile long from east to west and rising about 3,000 feet above both the Tokositna and Kahiltna Glaciers."

After the crash, the pilot made two satellite calls to Talkeetna, reporting injuries but the extent of those injuries are unknown, wrote Belcher. "Two subsequent satellite calls were initiated from the aircraft, but the satellite connection dropped and no sound was transmitted."

Flights to assess the site were attempted Saturday evening and Sunday morning with pilots reporting a low-cloud ceiling.

The National Park Service, as well as K2 Aviation, are both helping with the search, according to Olmstead.

An Air Guard HH-60 Pave Hawk and pararescuemen from the 210th, 211th and 212 rescue squadrons are in Talkeetna, en route to the crash site.

"When weather permits, a four-member ground crew will stage near the base of Thunder Mountain to provide weather observations and assist in the event of a short-haul or military hoist rescue," wrote Belcher. "A ground ascent of Thunder Mountain is not considered an option due to significant rockfall and unstable snow and cornice conditions at this time of the year,"