Four men, ages unknown, were critically injured by an electrical explosion in Catherine drive in Sandton on Saturday, ER24 emergency services said.

Spokesperson Werner Vermaak said the four men were working on an electricity box near the road around 3.45pm when it exploded, causing extensive burns to their upper bodies and extremities.

The road was closed off and paramedics on scene were waiting for an air ambulance (helicopter) to land.

Three of the men would be taken to nearby hospitals by road while the fourth one would be taken by air.

The cause of the explosion was not yet known, Vermaak said.

Sapa