Watford Police Station has been evacuated after a member of the public handed a "grenade" into the enquiry desk.
The building, in Shady Lane, has been completely evacuated and the bomb squad is on route after the item, described as a "smoke cannister" was brought into the station at 11.32am.
A cordon has also been put in place around the building, which is adjacent to Watford Magistrates Court.
It is not known how long the cordon will be in place.
A police representative said: "Someone brought it some sort of old grenade. It's something that's been found and as a precaution we've had to evacuate the building.
"This sort of thing happens all the time."
