The connection loss was reported at 6am to provider Kabel Deutschland.
A technician for the firm found that a cable duct containing 400 fibre optic cables providing tens of thousands of homes in the capital had been deliberately cut.
The western districts of Charlottenburg, Spandau and Wilmersdorf were worst hit by the black-out.
“Investigations are continuing,” Berlin police said in a statement on Sunday.
Kabel Deutschland said they were ruling out an accident. They said most homes had their connections back by 9pm.
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