Relatives of Gillian March, 37, were by her hospital bedside after she suffered a suspected drug-induced heart attack while partying at the island’s Amnesia nightclub last Friday.
She failed to come out of a coma and passed away on Wednesday morning, it emerged earlier today.
Tests conducted after she was admitted to Can Misses Hospital in Ibiza revealed traces of alcohol and the illegal drug crystal meth – which can affect the nervous system.
Doctors are still trying to establish if the combination of the drug and alcohol led to her death and tissue samples are due to be sent to a specialist laboratory in Barcelona.
An official investigation is now under way, which involves local court officials and police.
A Spanish-based source close to the investigation said Mrs March had died at about 11am on Wednesday.
The source said: “She was breathing with a machine and was still in a coma when she died. Relatives were at her
“A toxicology test carried out after she was admitted to
hospital is now in the hands of the court investigating her death and will be used to help establish if the drink and drugs that showed up caused her death.”
A Foreign Office spokesman said: “We can confirm the death of a British national in Ibiza on 11 September. We are providing consular assistance to the family.”
The dead woman is believed to have been on a night out with her husband when she fell ill.
Mrs March died the same day as another British tourist lost his life after falling from a hotel balcony on the neighbouring island of Majorca. Samuel Peter Hill, 22, thought to be from Beckford, Worcestershire, fell at a hostel in Magaluf and landed on his head.
The accident happened at about 3.30am yesterday at the Villasol Hostel, close to the Punta Ballena strip, where most of the resort’s nightclubs and bars are.
Earlier this year, father-of-three Craig Knapp, 31, from Dundee, killed himself by jumping to his death from a tenth-floor balcony in Magaluf after leaving a suicide note on Facebook.
Wife Lisa – mother to Craig, 12, Rhys, six, and Dara, four – told later how he flew to Majorca after dumping his lorry while he was out working, and was seen “drunk and depressed” shortly before he was found dead.
Mother-of-two Janine Mallett, 31, from Stockton-on-Tees near Middlesborough, was found floating dead in the sea off the island’s town of San Antonio in July after a night out with a friend. Tests showed she had consumed ecstasy, cocaine, speed and crystal meth.
The former Churchill insurance worker, who lived with her electrician husband Iain and two children, Jack, five, and Evelyn, three, had travelled to Ibiza with a female friend.