Police found traces of explosives in the apartment in the Fritz-Heckert neighborhood, Bernhardt said. They asked local residents to remain indoors.
"The cordoned-off area is so wide that we can almost rule out a threat to the local population," he said.
Bernhardt said it was unclear how many suspects were involved or what the motive of the planned attack was.
In late July, Islamic State claimed responsibility for attacks on a train near Wuerzburg and at a music festival in Ansbach which wounded 20 people.
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