Adjacent properties were affected by smoke in the incident at Clos de Baugy in the Vale.
The Guernsey Fire and Rescue Service and the police were despatched at about 2pm to the blaze, which had caused a huge plume of thick black smoke that was visible for miles around.
Many islanders called the the emergency services, leading to the line being jammed at one point: 'I tried calling 999 but it was engaged,' said passer-by Scott Tostevin, who was out for a walk when he smelled the fumes and saw the smoke billowing from behind the properties.
He said he could see that although the houses were not burning, the heat had melted the plastic gutters.
Fire Service watch commander Tom Chapman said that two tenders and a command vehicle were sent to the scene along with 10 personnel.
'Two fuel tanks were involved,' he said. 'It was an established fire when we arrived, impacting on two properties.
'We did not have any information as to whether there were persons inside those properties.'
It turned out that nobody was in either home at the time, but Mr Chapman said that smoke had got inside the buildings.
Had there been windier conditions and it been night time things could have been worse: 'This reinforces the importance of having smoke alarms,' he said.
He was unable to say what might have started the fire.