The German news agency dpa reported the bomb was defused, as planned, underwater on Sunday, which led to a loud detonation and a big water fountain on the river.
Police told dpa "the bomb is no longer a danger."
Firefighters had discovered the American 250-kilogram (550-pound) bomb during diving training in the river on Tuesday.
Even more than 70 years after the end of the war, bombs and other munitions still turn up regularly in Germany, a testament to the ferocity of the fighting in World War II.
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