Police have been called to Lincoln Castle after two suspicious packages were found, causing Lincoln Crown Court to be evacuated.
The report of two suspicious packages was issued to police at 1.04pm on Monday, who are in liaison with the explosive ordnance disposal team about the incident.
As a precaution, a 100 metre cordon has been put in place and Lincoln Crown Court has been evacuated.
Officers say that their investigation is likely to be ongoing for a number of hours and is likely to cause disruption, so police are asking people to avoid the area whenever possible.
If you have any information that may help with the investigation, call 101 and quote reference 202 of September 20.
It is the second bomb threat in Lincolnshire in the same day, as three schools in Spalding were evacuated as a precautionary measure.