Police have tweeted a picture of where the mortar has been discovered

Police in Preston have cordoned off an area around the Old Tram Bridge in Avenham Park, due to what is understood to be an unexploded bomb.

The military have been called in after two people metal detecting in a field opposite Avenham Park found what they believe to be an old military mortar.

Preston Police were called at 4.02pm by the metal detectors. The mortar is three inches in size.

A controlled explosion is “imminent” according to police at the scene at 7.15pm. People living near Avenham Park have been advised they will hear a loud bang when the detonation takes place. The mortar has now been detonated in a controlled explosion.

Police officers at the scene

The cordon on the south side of the Ribble is being expanded slightly to ensure safety.

Sergeant Paul McLernon posted updates via the Preston Area Police Twitter account about the find.

He said: “No access to Avenham Park from South Ribble via tram bridges. No access along the river bank in Avenham Park.”

Below is the area where police say the mortar is located.

Overhead view of where the device is located… pic.twitter.com/3qRIdQWWvf

— Preston City Police (@PrestonPolice) April 25, 2015

Police are advising members of the public to stay away from the area until further notice. The cordons were lifted shortly before 8pm on Saturday.