No injuries were reported at the building, known locally as the Kehlsteinhaus, while police said a ‘suspicious person’ has been taken into custody.

German police have detained a suspect after a fire engulfed the Eagle’s Nest, Adolf Hitler’s notorious Nazi-era mountain retreat in Bavaria, prompting an overnight emergency operation involving about 200 firefighters.

No injuries were reported at the building, known locally as the Kehlsteinhaus. Police said investigators were examining whether a “suspicious person” taken into temporary custody was connected to the blaze.

The fire alarm was triggered by a smoke detector at about 9:50pm (19:50 GMT) on Friday. Emergency crews could see flames rising above the building as they approached and found it “completely ablaze”, according to police.

The retreat’s remote Alpine location, at an altitude of more than 1,800 metres (about 6,000 feet), complicated efforts to extinguish the fire, police spokesperson Lisa Maier said.

While authorities have not announced a cause, German media reported that investigators suspected arson.

The newspaper Bild said emergency responders had encountered a motorcyclist travelling towards them on their way to the scene and that he was subsequently detained. His possible involvement remained under investigation.

Maier said inquiries were continuing, with police planning a news conference later on Saturday.

Built between 1937 and 1938, the stone-and-granite retreat stands on the Kehlstein mountain above Obersalzberg, near Berchtesgaden in southern Germany.

Designed as a monument to Hitler’s rule and a setting for receiving foreign diplomats, it offers sweeping views across the Bavarian Alps. Hitler himself visited the resort.

The site, which remains part of the legacy of Nazi Germany, survived World War II undamaged. It has operated as a restaurant since 1952 and also houses an exhibition examining its Nazi history.