German police said Saturday they had detained a suspect after a fire at Adolf Hitler’s former mountain retreat, known as the Eagle’s Nest, in the state of Bavaria.

About 200 firefighters were deployed to tackle the blaze at the Nazi dictator’s remote and difficult-to-access Kehlsteinhaus residence, on the peak of Obersalzberg in southern Germany.

Firefighters saw flames rising high into the air as they approached the scene, only 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 blaze.

Police spokesperson Lisa Maier said firefighters struggled to tackle the fire due to its location at an altitude of 1,834 metres (6,000 feet).

The building was only accessible with “heavy breathing apparatus”, she said.

Authorities were alerted to the fire on Friday evening, when a smoke detector triggered a fire alarm at about 9.50pm (1950 GMT), police said.

No potential reason for the fire was given, but the German media reported that the investigators suspected it was the result of arson.

As snow fell on the Alpine peak, the Eagle’s Nest was still engulfed in flames in the early hours of Saturday, a weather camera showed.

Officers blocked access to the road leading to the retreat, according to an AFP photographer.

The firefighters found no one inside the building.

Maier said police were still investigating but will hold a news conference later on Saturday.

German tabloid Bild reported that the authorities had arrested a motorcyclist they came across on their way to the scene.

Built between 1937 and 1938, the Eagle’s Nest forms part of the toxic legacy of Hitler’s Third Reich, which was responsible for the deaths of millions of Jews as well as Roma, LGBTQ people and Communists in the Holocaust.

It was designed to serve as a monument to Hitler’s rule, although the dictator rarely visited the complex.

It survived the second world war undamaged, and since 1952 has hosted an exhibition recounting the house’s Nazi history and a restaurant.