About 200 firefighters were deployed on Friday night to tackle the blaze at the Nazi dictator’s remote, purpose-built Kehlsteinhaus residence, a protected building on the peak of Obersalzberg in southern Germany, the Guardian reported.
Flames rose high into the air as firefighters approached the scene to find the building “completely ablaze”, police said.
“A suspicious person was taken into temporary custody,” they said in a later statement, adding that nobody was injured in the fire.
Lisa Maier, a police spokesperson, said firefighters struggled to tackle the blaze due to its location at an altitude of 1,834 metres (6,000ft).
The building, which was one of the few undamaged monuments of the Hitler era, was only accessible with “heavy breathing apparatus”, she said.
Built by the Nazis and formally inaugurated by Hitler on his birthday in 1939, the Eagle’s Nest has been preserved as a monument to “the insanity of the regime”, according to its website.
It is only accessible via a road cut into the mountain through previously impassable terrain. Nazis would enter a tunnel and take a 124-metre brass lift buried in the mountain to get inside the building.
Authorities were alerted to the fire when a smoke detector triggered a fire alarm at about 9.15pm, police said. When firefighters arrived on the scene at about 9.50pm, the entire building was engulfed in flames.
No reason for the fire was given, but German media reported that investigators suspected it was the result of arson. Firefighters found no one inside the building, which was reportedly still burning at 7am on Saturday.
Fire departments from six municipalities sent emergency personnel to tackle the blaze and the Bavarian Red Cross, the local mountain rescue service and the police also attended.
The blaze appeared to be out later on Saturday morning, although smoke continued to rise from the building.
A police spokesperson told the German tabloid Bild: “It is damaged to a large extent. The house is unlikely to be saved.” Officers blocked access to the road leading to the retreat, according to an Agence France-Presse photographer.
Maier said police were still investigating and would hold a news conference later on Saturday.
According to Bild, a motorcyclist whom local police officers came across on their way to the scene had been arrested, but his involvement in the fire remains unclear and a police spokesperson declined to release information about his identity.
The Eagle’s Nest was constructed between 1937 and 1938.
It became legendary in the postwar period and was often depicted as an essential meeting place in US war films, although in reality Hitler rarely visited the complex.
Since 1952 the building has housed an exhibition by the Institute for Contemporary History recounting its Nazi history, and a restaurant.