An engineer who was repairing a gas main that blew up on a business park in Whitstable is in hospital with burns to his face and legs.
Emergency crews were called to the blaze at the Estuary View Business Park around 10pm on Friday.
Southern Gas Networks (SGN) said its team of engineers had been called earlier that afternoon to fix a damaged pressure main, when the gas ignited.
One man, in his 50s, was taken to the William Harvey Hospital, 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'' by the explosion.
Kent Fire and Rescue said SGN had isolated the gas main shortly before 3am. A spokesman said: "It is not known what caused the explosion at this stage.''
So far SGN's teams have switched off supplies to more than 400 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.
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