Fire fighters put out five blazes in the town of Westerland on the island on Friday night alone, including one in a container, another in a barn and a third in the entrance to a pub.
Another fire could have become much more serious when 13-year-old holidaymaker Andreas Reuß heard the garden gate of his holiday home slam shut, smelled smoke and came out to investigate, only to find a fire burning in the thatched roof.
“There were 14 people in the house – one does not even want to consider what could have happened,” said Hauke Block, head of the Sylt fire services.
A series of fires were set on Tuesday – initially ascribed to lightning strikes – with fire fighters called to seven sites within a few hours. The most serious completely burned down the main building of the Klappholttal high school.
The arson attacks have provoked uncertainty on the island, with many property owners taking additional security measures around their buildings.
A local street party in Westerland was closed earlier than planned on Saturday so that people could get home before it got dark, organisers said.