Toxicology tests reportedly indicate that Gillian March, 37, had consumed alcohol and a drug known as crystal meth, which affects the nervous system, before she was taken ill during a night out with her husband on the party island last Friday.
Mrs March died at 11am on Wednesday, surrounded by her relatives.
She had been in a coma at the Can Misses Hospital in Ibiza since being rushed there by ambulance from the famous Amnesia nightclub, but failed to wake up and succumbed to a heart attack.
Unconfirmed reports claim tests conducted after she was admitted to the hospital revealed traces of alcohol and and the illegal drug, crystal meth, made famous by the television series, Breaking Bad.
An autopsy was due to take place yesterday morning to determine the cause of death.
Tissue samples will also be sent to a specialist lab in Barcelona to help experts reach their final conclusions for an investigating magistrate now in charge of a judicial probe into Mrs March's death.
Ibiza has a reputation as a party island with many clubs playing music from the dance scene.
Large amounts of alcohol and drugs have been associated with the island since the mid-1980s.
A source said: "She was breathing with a machine and was still in a coma when she died. Relatives were at her bedside.
"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 September 11. We are providing consular assistance to the family at this difficult time."
The tragedy comes just weeks after Ibiza's drug scene hit the headlines when Melissa Reid, from Lenzie in East Dunbartonshire, was arrested in Peru for alleged drug smuggling.
The 19-year-old - who has since turned 20 - and Irishwoman, Michaela McCollom Connolly, were caught trying to board a flight to Madrid with £1.5m of cocaine in their suitcases.
The pair had been spending the summer working and partying in Ibiza, where they claim they were taken hostage by drug dealers and forced to travel to South America.
They are still in jail in Peru waiting to see how prosecutors are going to deal with the case
Mrs March died the same day another British tourist lost his life after falling from a hotel balcony on the neighbouring island of Majorca.
Samuel Peter Hill, 22, from Worcestershire, was killed almost instantly after falling from a hostel in Magaluf and landing on his head.
The freak accident happened around 3.30am on Wednesday at the Villasol Hostel, close to the Punta Ballena strip where most of the resort's nightclubs and bars are.