Leicestershire Police confirmed Thurcaston Road had been closed in between the junctions with Abbey Lane and Loughborough Road while officers attend an incident. According to reports by Leicester Media, a bomb disposal team was called to the scene after a device pulled out of the river Soar.
Leicestershire Police said that a mortar had been discovered by magnet fishers.
Homes and businesses nearby were evacuated and surrounding roads have been locked down by police.
Thurcaston Road runs over the river Soar, in the Belgrave area to the north of the city.
Abbey Lane, or the A6, is the northerly road out of Leicester city centre.
A Leicestershire Police spokesperson said earlier this afternoon: "An area around Thurcaston Road in Leicester has been cordoned off after an item believed to be a mortar shell was discovered by magnet fishers in a river.
"Explosive Ordnance Disposal (EOD) are at the scene to examine the find.
"In the interests of officer and public safety a 100 metre cordon has been placed around the area. Thurcaston Road is closed between its junctions with Loughborough Road and Abbey Lane and a small number of homes and businesses have been evacuated.
"Motorists are being advised to avoid the area while emergency services deal with the incident."
As of 12.30pm, the two roads had been cordoned off at their intersection.
However, the force confirmed that by 2.30pm the roads had been reopened "as well as all side streets and park footpaths".
The river Soar runs through Leicester, however the area affected is near where the river runs through a series of lakes and reserves, as well as Leicester Marina.
Magnet fishing is the use of powerful magnets to pull metal objects from waterways, such as rivers and canals.
The hobby is a combination of environmentalism and treasure-hunting.
While the magnets are usually strong enough to lift out human debris such as bicycles, shopping trolleys and car parts, magnet fishers are usually in search of valuables and safes.
However, it has also been known to find dangerous objects, posing a risk to those undertaking the pastime.
Magnet fishers have been known in the past to have found discarded guns and explosive devices.
More to follow...