The family of Abbey Conner, a Wisconsin student who died at a five-star Mexican resort after drinking shots in celebration of finishing her exams, are demanding to know what happened in her final hours.

The 20-year-old was found floating face down in the swimming pool at the Iberostar Paraiso del Mar resort in January. Her death certificate recorded it was an “accidental drowning.”

Her brother, Austin Conner, who was with her at the time of the incident, said they were celebrating the end of their final exams in January and each drank four or five shots of tequila at the pool bar.

After this, the 22-year-old recalls they drank more shots with a group of young men and has suspicions the drinks were spiked.

The next thing Mr Conner remembered was waking up in an ambulance on the way to hospital after he and his sister were discovered unconscious in the pool.

“I’ve been in college for five years and had my fair share of drinks before," he told the Journal Sentinel. "No way in hell I’m putting my face down in a pool and going to sleep.”

He added: “Knowing that we got played or are victims of some sick person drugging us is almost surreal.”

Their father, Bill Conner, suggests that the drinks were tampered with. “Somebody had to slip them some type of drug.”

Austin Conner recovered after being treated in hospital, but Ms Conner never regained consciousness. She had a broken collarbone and had anoxic brain injury as well as cerebral edema, according to her medical reports.

Toxicology reports taken at the Playa del Carmen medical centre showed that her blood-alcohol content was 0.25. At this level of intoxication, effects can include nausea, vomiting and a “loss of consciousness” according to BreathKey Breathalyzers.

Ms Conner was moved to a Florida hospital where she was declared brain dead. Her family later decided to remove her ventilator.

The family have hired a lawyer to investigate further what happened to their daughter. “It’s all too convenient,” lawyer Florentino Ramirez said.