Concerns following discovery of suspicious packages at Lincoln Castle
Three Spalding schools also received bomb threats
Lincoln Castle will remain closed this morning after two controlled explosions were carried out yesterday afternoon.
Police and bomb disposal experts were called after suspicious packages were found in the grounds.
Officers say they're satisfied the items were not explosive devices.
Meanwhile pupils at three schools in Spalding will return back to the classroom following what police describe as malicious and unfounded bomb threats.
Lincolnshire police have thanked staff at Spalding High School, St John the Baptist Primary and Monkshouse Primary for their swift efforts in a difficult situation.
Officers say at this stage they don't believe there's a connection between the two incidents.
Yesterday people in the Castle grounds were evacuated.
That included those who were at the Crown Court at the time.
Police say "our investigation is likely to be ongoing for a number of hours and will cause some disruption in the area."
That's likely to continue for some time today.