Image caption The Aston Expressway, which links Birmingham city centre to the M6 at Spaghetti Junction, has been shut since Monday morning

A large unexploded World War Two bomb has shut one of Birmingham's major roads and forced the evacuation of "hundreds of homes" and businesses.

The closure of the A38 (M) Aston Expressway is causing long delays for drivers. It is likely to remain closed until Tuesday, police said.

Rail services on the Cross City Line between Lichfield and Birmingham have all been cancelled.

The 500lb (227kg) device was found at a building site in Priory Road, Aston.

A 500m cordon was set up after its discovery at about 09:45 BST. Police have warned it may have to be widened as investigations continue.

Bomb disposal teams have been in attendance at the scene throughout most of the day.

The device has been identified as a German-made shell, a police spokesman added.

Image copyright West Midlands Ambulance Service Image caption Paramedics tweeted a photo of the bomb, which is believed to have been made in Germany

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The Aston Expressway links the city centre with the M6 and other major routes in north Birmingham.

All exit and entry slip roads of the M6 at junction six are closed.

Image caption Bomb disposal teams have been at the scene for several hours

Cdr Chris Johnson of West Midlands Police said: "An initial assessment from Army bomb disposal suggests this is a large explosive device − that's why an extensive cordon has been put in place.

"There is the possibility we may have to extend the cordon on advice from expert. We don't take decisions like this lightly but public safety has to be our number one priority.

"Hundreds of homes have been evacuated and we are working with our partners to provide emergency accommodation."

Mr Johnson said there had been some difficulties in accessing the device because of the terrain and the bomb's position at the construction site.

Image caption Drivers have faced long delays as roads have been closed for several hours

Those people removed from their homes are being offered sanctuary at the Aston-Newton Community Seventh Day Adventist Church in Lichfield Road.

London Midland said its rail services between Birmingham New Street and Lichfield Trent Valley would be cancelled for the rest of Monday.

It has advised passengers to use alternative transport as its rail tickets are being accepted on local National Express West Midlands bus routes.

National Rail said earlier the disruption was set to last all day.

Image caption Several roads in the area were blocked off by police

Image caption All exit and entry slip roads of the M6 at junction six are closed