The Queen Elizabeth II Bridge at the Dartford Crossing was closed after a suspected World War Two bomb was found nearby.
The device was discovered shortly before 9am on Tuesday and a Ministry of Defence bomb disposal team was sent to the scene, Essex Police said.
Motorists were caught up in huge queues on the roads surrounding the bridge following the discovery.
The bridge has now re-opened and the bomb disposal team has confirmed it was an empty shell with no explosives inside.
A spokesman for Essex Police said: “The MoD bomb disposal team has assessed the unexploded bomb and have confirmed it is an empty shell casing with no explosives inside.
“It will now be taken away from the site and there will be no need for any further closures to the QEII Bridge.”
It comes after a 500kg World War two bomb was discovered in the Thames near London City Airport on Sunday.
A 214-metre exclusion zone was set up causing dozens of flights to be cancelled and homes in seven streets to be evacuated.
It was lodged in silt about 11 metres (36ft) underwater and removed by Royal Navy divers on Monday night, before being taken into the Thames estuary to be detonated at depth off Southend.
Essex Police tweeted to confirm that the discovery of the bomb near the Dartford Crossing was unrelated.
A spokesman said in an initial statement: “We are on scene at an industrial estate in Oliver Close, Grays after an unexploded World War II bomb was discovered.
“We were called at around 8.55am today.
“The Queen Elizabeth II Bridge was closed for a short time but has re-opened.
“A Ministry of Defence bomb disposal team is on the way and the bridge may be shut again when they dispose of it.”