Police said on Monday that a 17-year-old boy was arrested for one of the fires, a car torched on Jorisvej in Amager.
The teen was reported to the police after acquaintances noticed that he had suffered burns.
"He simply burned himself. We were contacted by people who know him, who could tell us about his burns," Copenhagen Police inspector Jens Møller Jensen told TV2.
The teen appeared in court on Monday and admitted to the Amager fire, news agency Ritzau reported. The 17-year-old denied, however, that he had torched the car on behest of another, which police believe is the case.
Although this is now the second arrest in connection to the fires, they show little sign of slowing down.
On Monday, Møller Jensen told TV2 that investigators are working on several different theories.
The first is that the car fires and their media coverage have had a snowball effect that has inspired others to do the same. Another possibility is that one or more perpetrators are engaged in what investigator Møller Jensen called “an exciting game with the authorities”.
“We are looking at the times and locations [of the fires] and trying to establish a pattern,” he told TV2.
The investigator said that police are also considering the possibility that some of the incidents are actually insurance scams in which car owners are using the spate of car fires to provide a viable cover for torching their own vehicles in order to get an insurance payout.
“I think however that that could only be a very small part of it,” Møller Jensen said.
He said an investigation unit has been established and that police have increased both video surveillance and night patrols in hopes of putting an end to the arson.