Police divers are carrying out a search of a lake in Old Basford following reports that a gun could have been discarded there.
Acting on a tip-off from the public, Notts Police's underwater search team have begun scouring the water at Vernon Park.
DCI Louise Jordan said: "We have received information that a weapon could have been discarded in the water.
"As with any suspected firearms activity we have taken this report extremely seriously and are carrying out the necessary searches to determine if a weapon has been concealed in the lake."
Witnesses, or anyone with information about firearms activity, is asked to call Nottinghamshire Police on 101 or Crimestoppers anonymously on 0800 555 111.
