Hundreds of residents had to be evacuated from the center of Munich last night after German authorities were unable to defuse a 550lb. WWII-era bomb found buried a few feet underground.

Though there are tens of thousands of unexploded munitions littering the country, this US Air Force bomb was unusual because it required a controlled detonation.

The explosion occurred around 10 PM local time, and the resulting blast blew out windows in the surrounding area and started a few small fires. No injuries were reported, and most residents have since been allowed to return to their homes.

Experts say this latest incident could be a sign of things to come. As one former bomb disposal chief told Spiegel Online, "unexploded bombs are becoming more dangerous by the day through material fatigue as a result of ageing and through erosion of safety elements in the trigger mechanisms."

The threat extends beyond Germany to neighboring countries, where similar bombs were dropped during the war. The discovery of an unexploded WWII bomb forced Amsterdam's Schiphol airport to shut down one of its terminals this morning, and several flights were either canceled or delayed.

[videos via @Alex_Ogle]