The Yorkshire Evening Post understands that a grenade has been found by a man who was magnet fishing in the River Aire.
Pictures and video show the large police presence in the area.
A cordon has been placed across a number of roads and footpaths.
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The public have been warned to stay away from the area.
One eyewitness said: "There was a chap using a magnet to pull metal out of the river.
"Police are awaiting for the bomb squad to arrive."
A West Yorkshire Police spokesperson said: "Closures are in place around Crown Point Road after a member of the public reported finding what was believed to be a grenade at around 1.23pm today.
"Enquiries are ongoing at the scene and the Explosive Ordnance Disposal team have been requested to attend.
"People are requested to avoid the area at this time."