Two Americans who were on vacation in Mexico were found dead in their hotel room on Tuesday, June 13, after apparently being “poisoned” by an unknown substance.

The couple, identified as 28-year-old Abby Lutz and 41-year-old John Heathco were staying at the luxury hotel Rancho Pescadero in Baja California Sur.

Paramedics were called to the couple’s hotel room after receiving a report that they were unconscious, according to ABC News.

However, once the paramedics were checked, they determined Lutz and Heathco were unresponsive and did not have vital signs.

Now, Lutz’s family is speaking out, believing the two suffered from carbon monoxide poisoning.

Here’s everything we know so far.

What happened?

Lutz and Heathco were on vacation together in Baja California Sur, according to a statement in a GoFundMe started by one of Lutz’s family members.

The two were staying at the Rancho Pescadero, a luxury hotel and Hyatt property located in El Pescader, approximately 40 miles north of Cabo San Lucas.

Lutz and Heathco began to experience symptoms they thought were consistent with food poisoning and went to the hospital for treatment during the trip, according to Lutz’s GoFundMe.

The couple started feeling “much better” several days later and by Monday (12 June) were back at the hotel and communicating with their families.

Just one day later, their families received phone calls saying they had “passed away peacefully” in their hotel room in their sleep.

Paramedics in the area responded to a report of two unconscious people in the hotel and arrived around 9pm on 13 June.

The Baja California Sur attorney general’s office said in a statement that the two died of poisoning by an unknown substance and had no signs of physical violence. They said the two had been dead between 10 and 11 hours by the time they arrived.

Lutz’s family said they were told the deaths were “due to improper ventilation of the resort and could be carbon monoxide poisoning”.

One of the first responders, Fernando Valencia, said that he and his partner felt “dizzy” when they entered the room where Lutz and Heathco were staying.

“We went out of the room as soon as possible… I was afraid for my partner because my first thought in my mind was ‘are we going to die?’” Mr. Valencia told Good MorningAmerica in an interview.

Mr. Valencia called it “one of the worst experiences.”

Henar Gil, the general manager of Rancho Pescadero said in a statement provided to The Independents: “We are truly heartbroken by this terrible tragedy. Our hearts are with the impacted families and loved ones during this unimaginable loss.”

“Local authorities are still actively investigating the situation, and the safety and security of our guests and colleagues remains a top priority, as always. We can confirm there is no evidence of violence related to this situation, and we are not aware of any threats to guests’ safety or wellbeing,” Ms Gil said.

She added “We are working to care for those who have been impacted and we are working closely with authorities as they conduct their investigation to understand the cause of death. Further inquiries should be directed to local authorities.”

US Department of State spokesperson Matthew Miller said they are “closely monitoring the investigation” into Lutz and Heathco’s deaths in a news conference on Thursday (15 June).

“We stand ready to provide any consular – any appropriate consular assistance,” Mr. Miller added.

Current and former employees of the hotel have voiced concerns, alleging that the hotel knew about gas leak problems and even disabled the carbon monoxide alarms.

Ricardo Carbajal, the former night manager of Rancho Pescadero told The Los Angeles Times: “They knew there were problems with a gas leak.”

He added: “Everyone was aware of the alarms and that the detectors were off.”

Mr Carbajal, who stopped working at the luxury hotel in March, said carbon monoxide detectors went off frequently over a period of three months last year before hotel managers disabled the alarms due to noise complaints.

Current employees of the luxury hotel told The Los Angeles Times that there were complaints of a “strong smell of gas” from employees and guests but hotel managers ignored it.

“Housekeepers reported gas leaks, security reported gas leaks maintenance workers reported gas leaks,” said one employee who requested to remain anonymous.

Who are the victims?

The victims are Abby Lutz and John Heathco.

According to the GoFundMe description, they were dating at the time of their deaths.

Lutz, 28, was from Newport Beach, California but grew up in Idaho, her aunt, Karen Lutz, told The Daily Beast.

According to Karen, Lutz loved traveling and had previously visited Europe, Asia and Mexico.

“Abby was supposed to meet up with her dad this week for Father’s Day,” the GoFundMe description for Lutz says. “Abby was the most beautiful soul and we will miss her so much.”

Her family is asking for help in bringing her home so they give her a funeral.

Heathco owned a health supplement company in Newport Beach, according to his LinkedIn profile. It is unclear where he is from originally.