Some 300 people were evacuated from Kiwi House, the official New Zealand support centre at the London Olympics, after it caught fire on Wednesday night, British media reported.
The fire broke out when two gas cylinders connected to a barbecue exploded at around 7:30 pm London time (18:30 GMT), firefighters were quoted as saying.
No one was hurt in the fire, reports said.
Kiwi House staff wrote on Twitter that they had a "rather large fire” in the outdoor barbecue area. The fire has now been put out, the ITV News television network said on its website.
The Kiwi House is located in the King's Cross district of central London.