Police said they were doing everything they could to stop the attacks, which have become a regular feature of life in the capital. Investigators believe there may be a political motive to them.
The first fires Tuesday night started at about 11 pm in Berlin-Spandau, Charlottenburg and then tracked to Friedrichshain.
Most of the arsons on Tuesday night and early Wednesday morning appear to have been centred in Charlottenburg.
On Monday night 11 cars were set alight, while nine cars were burned last Wednesday.
Since the beginning of the year, officials have registered about 80 auto arson cases.
It's not known exactly what's behind the burnings, although they appear to be some kind of leftist or anarchist political statement, since expensive vehicles are generally the main targets.
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Police have struggled to develop leads as the arsons appear to have spread beyond a few criminals to become a general trend.