BERLIN — Residents in two German cities are evacuating their homes as authorities prepare to dispose of World War II-era bombs found during construction work this week.

About 21,000 people have been ordered to leave their homes and workplaces in the western city of Koblenz as a precaution before specialists attempt to defuse the 500-kilogram (1,100-pound) U.S. bomb Saturday afternoon.

Among those moved to safety are prison inmates and hospital patients.

Officials in the financial capital Frankfurt, meanwhile, are carrying out what is described as Germany’s biggest evacuation, though similar operations are common even 72 years after the war ended.

More than 60,000 people have been ordered to leave a radius of 1.5 kilometers (nearly a mile) around the site where the 1.8-ton British bomb will be disposed of Sunday.