Tens of thousands of German residents in Frankfurt are being told to evacuate by Sunday morning for authorities to defuse a World War II-era bomb.
A Frankfurt police spokesperson said as many as 70,000 people could be affected, according to The Local Germany, which would make it Germany's largest evacuation since World War II.
"Due to the large size of the bomb, extensive evacuation measures must be taken," Frankfurt police said. They tweeted a map of the circular evacuation zone, an area which stretches slightly over 3 kilometers, or about 1.8 miles, at its longest on the map.
Police said the bomb was discovered during construction work on Tuesday in the city's Westend district, but that it's not "currently" dangerous.
The bomb is called an HC 4000 and contains more than 3,000 pounds of explosives, police said in a statement. It's likely a British bomb dropped during a World War II bombing raid, Deutsche Welle reports.
Finding unexploded ordnance in Germany is relatively common, and certifying a site as free of buried weapons is a prerequisite for construction, according to DW. The U.S. and U.K. dropped more than 1.3 million tons of bombs on Germany during World War II, Smithsonian Magazine says, with about double that number on Europe as a whole.
Up to 10 percent of those bombs have not exploded, according to the magazine.
In May, 50,000 people had to be evacuated from the German city of Hanover while technicians defused three British bombs found there. On Christmas Day last year, about 54,000 people had left their homes in Augsburg. That was the biggest evacuation in Germany since the war's end, DW reports.
Defusing the bombs is not without risk as well. Eleven bomb disposal technicians have been killed on the job in Germany between 2000 and early 2016, Smithsonian Magazine says.
There are thousands of unexploded bombs still buried around Germany. NPR's Soraya Sarhaddi Nelson says they become more dangerous over time as components break down.
NPR's Eric Westervelt reported in 2010 that in the German capital of Berlin alone, 4,000 "unexploded pieces of ordnance — mostly aerial bombs and artillery" were still undiscovered. At the time, about 7,300 bombs in Berlin had been "detonated successfully" since the mid-1980s, he said.
Unexploded bombs from World War II have prompted evacuations across Europe. More than 70,000 people had to evacuate from Thessaloniki, Greece in February. And bombs dropped during the German Blitz on London have stuck around there as well.