An engineer who was repairing a gas main is in hospital after suffering burns to his face and legs in an explosion.
Emergency crews were called to the incident at the Estuary Business Park in Whitstable, Kent, at around 10pm on Friday.
SGN said its team of engineers had been called earlier that afternoon to fix a medium pressure main, which had been damaged by a third party, when the gas ignited.
One man, in his 50s, was taken to the William Harvey Hospital in Ashford to be treated for non life-threatening injuries.
Another man was treated at the scene for minor injuries, South East Coast Ambulance Service said.
Images posted on Twitter showed huge flames coming from the gas main fire, with one witness who lives a mile away describing how the sky "lit up" after the explosion.
Kent Fire and Rescue said SGN had isolated the gas main shortly before 3am and put the blaze out.
A spokesman said: "It is not known what caused the explosion at this stage."
So far SGN's teams have switched off supplies to around 430 of the 600 affected properties in the area around Old Thanet Way.
In a statement, SGN said: "It is too early to know what caused the fire last night but an investigation is under way.
"We would like to reassure the local community that we are continuing to closely monitor the situation to ensure their safety."
A number of road closures are in place.