Patong hospital confirmed four people were dead - two males, and two sex unknown. The nationalities of the dead are yet to be identified.
Eleven others were injured, two of them severely.
The cause of the fire is not yet clear. Phuket deputy governor Chamroen Tipayapongtada was quoted by AFP as saying , "The fire was caused by lightning which struck a transformer and the fire spread throughout the place."
But Phuket News reporter Tanyaluck Sakoot, after talking with police and a member of the Tiger staff, said she had been told that the fire had started from an electrical short at the front of the building during torrential rain, and had then spread along power cables inside the building to the back, where the worst fire took place.
Two people who were in the nightclub both said the fire appeared to start from a new lighting rig, installed only a week or so before, which exploded.
Whether this was the case has not been confirmed, but the rig was removed almost as soon as the fire was extinguished. Forensic experts from Bangkok are expected to come down to try to pin down the cause.
The dead were found in the restrooms, apparently trying to escape from the fire.
Ms Tanyaluck described distressing scenes at Patong Hospital,where the injured were taken for initial treatment. She spoke with Benjamin Tallanotte, 30, from France, almost entirely swathed in bandages with second-degree burns to 40 per cent of his body. Mr Tallanotte has been transferred to Bangkok Hospital Phuket burns unit.
"He was very distressed." she said. "He had tried to call his wife, who was in their hotel, but his phone was soaked and was not working." The Phuket News has since confirmed that Mrs Tallanotte has been contacted and is at her husband's bedside.
Five of the 11 people who were hurt were not burned, but were injured in falls during the scramble to leave by the main entrance steps or down the fire escapes.
Steve Johnston, of Phuket Live Radio 89.5, who was at Tiger at about 7:30, after the flames had been put out, described the scene as "surreal".
"The whole bar and soi is taped off. There are police all over the place, but all the emergency staff and firemen have left, so I guess they are satisfied that no one else is inside.
"There's a surreal calmness to the place. There are even people sitting quietly in the front of the place.
"There's still a little smoke, and a water tanker just came in to damp things down.
"You can't see any damage from Bangla Rd. The fire was apparently at the far end of the soi, off Bangla. It looks like the exits onto the soi were effective in letting many people escape."
Apart from Mr Tallanotte, one other person was kept in hospital - Ms Noodaeng Pramangkata, 42, listed as suffering from dizziness and hyperventilation.She remains in Patong Hospital.
The others listed, all of whom have now been discharged, are:
Ms Butsakorn Jesa'i, 31, second-degree burns.
Ms Kanyaporn Khanthong; 25, injured foot.
Mr Nicholas Robyn; 25, French national, injured arm.
Mr Mathieu Lagrange; 40, French national, injured hand and arm.
Ms Kanjana Suwanboon; 25, admitted with hyperventilation syndrome.
Ms Hong Nakorn; 30, injured leg.
Ms Suree Deeying; 32 , injured leg.
Ms Yasmine Khelaef-Humber; 31, French national, panic attack.
Mr Siwakorn Kaetsompong, 30, burns to both arms.