'Hesa Fredrik' is a loud siren designed to warn the public of immediate danger such as natural disasters or even war.
But it's unclear why the siren went off without warning in Bankeryd, north of Jönköping, on Monday.
Police and emergency services received a large number of calls from worried residents who heard the alarm, and a technician was working to look into the problem on Tuesday.
The alarm is officially called a VMA siren (viktig meddelande till allmänheten or important message to the public) but gets the nickname Hesa Fredrik from a Dagens Nyheter columnist.
Live tests of the system occur on the first Monday of March, June, September and December at 3pm. At any other time, it is supposed to be a warning of danger to the public.
Back in 2017, Hesa Fredrik was sounded by mistake in Stockholm, startling the city's one million residents on a Sunday evening.
That time, human error was behind the false alarm, and police and Sweden's Civil Contingencies Agency (MSB) were criticized for being slow to release information as their websites went down due to large numbers of people searching for information.
war – (ett) krig
unclear – oklar
emergency services – räddningstjänsten
by mistake – av misstag
to criticize – att kritisera
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