A main road in Norwich which was closed off, after an electrical fault caused an underground explosion, has partially re-opened.

Eastern Daily Press: Police block off the junction of Dereham Road and Old Palace Road in Norwich because of a possible gas leak. PICTURE: Dan GrimmerPolice block off the junction of Dereham Road and Old Palace Road in Norwich because of a possible gas leak. PICTURE: Dan Grimmer (Image: Archant)

The small explosion happened at a link junction between two electrical substations and has forced emergency services to close Dereham Road.

The blast blew up a manhole cover on the pavement opposite Tesco, where two people were walking.

They were not harmed, but were left shaken by the incident.

The incident happened at the junction with Old Palace Road and Heigham Road at just before 1.30pm today.

Eastern Daily Press: The manhole cover blown upwards by an explosion on Dereham Road. PICTURE: Dan GrimmerThe manhole cover blown upwards by an explosion on Dereham Road. PICTURE: Dan Grimmer (Image: Archant)

Emergency services were initially called to a suspected gas leak, but it turned out to be an electrical problem.

Fire crews from Earlham and Carrow went to the scene and isolated the area.

The nearby Tesco store was left without power and 65 properties had their power supply switched off later as engineers worked on repairs.

Police used blue tape to seal off the junction in all directions, while pedestrians were also prevented from walking in the area.

Rob Burling, watch manager for Norfolk Fire and Rescue, said: 'There's a link junction between two substations which has gone out.

'There were sparks and an explosion which has lifted a manhole cover up.

'Members of the public were around at the time. They were not hurt, but believe one may have suffered a panic or asthma attack.

'We have shut the roads off and isolated the area and we are now waiting for UK Power Networks to isolate the substations and start digging it out to repair it.'

Workers from the National Grid and UK Power Networks were at the scene.

The road opened at about 3.30pm, but with temporary lights and a one way system operating.