Managers at the plant decided to shut down the two reactors after indications on Saturday that rubber seals at the Forsmark 1 reactor showed possible damage.
Forsmark 2 was also taken off-line because the two plants are constructed similarly.
Both reactors have been plagued with problems, including brief shutdowns in December and last month.
Minister for Enterprise and Energy Maud Olofsson said on Friday that she wants a report from Vattenfalls board on what actions they will take to improve safety at Forsmark.
Olofsson also said she wants to be continuously updated on the measures taken since the government, as owner, has an overall responsibility for the energy group.