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22 April 2015 Last updated at 21:02 BST
Electrical equipment exploded underneath Stratford Road in Shirley on Monday, causing smoke and then flames to repeatedly shoot out of the pavement, in front of a row of shops and parked cars.
The passer-by managed to film the explosion on his mobile phone.
West Power Distribution said engineers were despatched after receiving a call at about 17:00 BST.
They isolated electricity supplies and cordoned off the area before repairing an underground link box.  A spokesman described the incident as very rare.
The surrounding footpath and tarmac was replaced on Tuesday.
A pedestrian has captured an underground explosion in a manhole in Birmingham where flames leaped several feet in the air.