Police were called at 9.32pm and cordoned off the road from the junction of Victoria Road North to the junction with Isambard Brunel Road.
At 10.45pm there were at least 11 police cars, three South Central Ambulance Service vehicles, and two fire engines present.
A spokesman said about the closure: ‘This is likely to be in place for some time and we advise you take an alternative route.’
The fire service and paramedics are also on the scene.
A white tent has been put up at a bus stop.
Several residents in surrounding streets say they heard a ‘really loud bang’ before emergency crews arrived.
One resident of Ivy Close said: We heard a really loud bang, but thought nothing of it. Living around this part of town you don’t think anything about a noise like that because you think it’s a made by a motorbike back firing.
‘But it was a really loud bang – people were saying they heard it all the way at Handsworth House.’
Police have asked any witnesses to call 101 with reference 2091 of today’s date.