A fire which destroyed a country house hotel in Argyll early yesterday is being treated as suspicious by police.

Dunans Castle in Glendaruel was devastated by the fire, which began just before 4am in the attic of the house and blazed for hours, destroying three floors and the roof space. Only the west wing escaped undamaged.

Twelve residents had to be evacuated from the house along with the owners, the Lord and Lady of the Manor of Marr. The guests escaped unharmed although one guest, a former marine, was hit by a hot beam while trying to put out the fire.

Strathclyde Police said yesterday that they had been unable to establish the cause. Forensic teams, assisted by the fire brigade, were beginning a search through the charred remains to determine whether the fire had been started deliberately.

''We are treating it as suspicious until we have established exactly what happened,'' said a spokeswoman for Strathclyde Police. She did not confirm allegations that the owners had received threats to destroy the castle last year.

More than 50 firefighters from across Argyll descended on the castle at the height of the blaze and trained five hose lines on the house.

But such was the ferocity of the fire that it was not declared under control until 10am.

Neil Snazel, 26, a former Royal Marine commando, tried to contain the blaze.

He was one of 10 staff from the Manchester office of NSB International, an IT recruitment firm, who were at the hotel on an activity weekend.

Mr Snazel and a colleague, Craig Holborn, were in the study when the fire alarm went off.

He said: ''Lord or Lady Marr turned it off but it kept repeating. Lord Marr asked if anyone was smoking, but no one was. He apologised and said it must be the battery.''

But on his way upstairs, Mr Snazel heard the fire was in the attic. ''I ran down the stairs to pick up the fire extinguisher and then ran up the stairs. I got to the attic door, but it wouldn't open. I stepped back and kicked it down.

''There was a big hole in the attic ceiling, like a man-made hole through the plasterboard. The fire was above the hole. The centre beam along the apex of the attic was on fire and spreading.

''Lord Marr had a carbon dioxide extinguisher for electric fires. I told him that was useless and to get one that would put the fire out. He disappeared off the scene and we didn't see him again.''

Mr Snazel tried to contain the fire. ''Basically, I soaked the whole area and I thought I'd put it out, but there must have been an air pocket and it all went up.''

He kicked the plasterboard to try to get the fire extinguisher through.

''One of the wooden beams fell through and burned my left arm near the elbow. I changed the fire extinguisher. Two minutes later, the roof collapsed and one of the lads pulled me out.''

Mr Holborn said: ''Lord Marr was running about trying to determine whether it was an alarm fault or a real fire. Eventually they located the fire in the attic and it was all hands on pumps.

''But we eventually had to leave. We weren't having any effect on it whatsoever.''

Mr Holborn said the guests were taken into the Glendaruel Hotel at about 5.30am. The hotel confirmed the castle's owners also took refuge there yesterday.

Dunans Castle, near Loch Fyne, was bought by the current owners 18 months ago. The couple, Robert Lucas-Gardiner and his wife, Ewa, bought their titles from the Manorial Society of Great Britain.

The house, which has been awarded AA five diamond status, offers a range of activities to its guests including a ''juice farm'' where guests can live on a diet of nothing but juice in a bid to rid their body of impurities.

The house dates back to the sixteenth century and was bought in 1746 along with the Dunans estate by Andrew Fletcher, head of the Fletcher clan. The main house was rebuilt in 1830, when a main tower was created.