An active World War II-era bomb was discovered during construction work in the inner courtyard of a popular museum in Munich, forcing staff and customers to evacuate.

The bomb, which weighs 550 pounds, was found near the entrance to the 90-year-old building around midday local time, revealed Deutches Museum spokesman Gerrit Faust today, according to the Star Tribune.

The Deutches Museum is one of the largest and oldest science and technology museums in the world.

Bomb disposal experts were called to the scene, and after the area was completely evacuated, they were able to successfully free the bomb, reported Yahoo News. However, since the detonator was still intact, the crew couldn't defuse it on-site. Instead, the experts plan to move the bomb off-site.

"The bomb in the Deutsches Museum could not be defused on the scene. It will be transported away in the evening," tweeted police.

A spokesman for fire services assured locals and the media that moving the bomb poses no danger due to its mechanical detonator.

"It would need a really hard impact to set it off," he said, according to German news site The Local.

Once off-site, the bomb will be destroyed in a controlled explosion.

Despite the war being over for 70 years, bombs are regularly found during construction in major cities like Munich and Berlin. Sometimes, they're even found in other European cities like London. The explosives were dropped by Germany during bombing runs, but failed to detonate.