With fear widespread in the city after a series of threats, parents were most likely dreading the start of a new school week. But at 4am on Monday a special police unit stormed an apartment in the centre of the northern city and arrested a suspect.
Police were confident they had apprehended the right person but stressed that they had not yet closed the investigation.
A manhunt began last Tuesday after the Reventlou primary school received an email claiming that manipulated marzipan hearts had been placed around the schoolyard.
The marzipan treats later found at the school were laced with a substance which experts said would cause health problems, though these would not be life-threatening.
The marzipan attack was linked to an extortion attempt, Kieler Nachrichten said. The blackmailer demanded €3 million from the Coop supermarket chain. The sum was to be paid out in the online bitcoin currency.
The as-yet unidentified extortionist piled further pressure on the retailer when bomb threats were sent by email to three more schools in the city.
Police deployed sniffer dogs and bomb disposal teams but no explosives were found at the schools.
According to the newspaper, the blackmailer linked the extortion attempt to the planned merger of Coop and Rewe, another German supermarket chain.
Police urged Kiel residents not to consume any foodstuffs found lying around in the city.