3 Americans found dead from carbon monoxide poisoning at Mexico City Airbnb

Three American tourists died from carbon monoxide poisoning while staying at an Airbnb rental in Mexico City last month, officials said.

The three were staying at a rental in a residential complex in the La Rosita neighborhood when they were found dead on Oct. 30, according to the Attorney General's Office of Mexico City, which investigated the deaths.

The victims were identified by relatives as Kandace Florence and Jordan Marshall -- both originally from Virginia Beach, Virginia -- and Courtez Hall, who was a schoolteacher in New Orleans.

The three friends were in town for Day of the Dead festivities when Florence called her boyfriend and said she wasn't feeling well, Florence's parents told "Good Morning America."

"She said, 'I was vomiting and dizzy and my legs are wobbly," her mother, Freida Florence, said.

Marshall's sister, Jasmine Marshall, told "Good Morning America" that she received a message from Florence's boyfriend on Instagram that mentioned he wasn't able to reach Florence for the rest of the day after that call.

"So that worried him," she said. "So he contacted the Airbnb host to do a welfare check and they were all found unresponsive."

Security guards at the complex detected an intense gas smell in the apartment and poisoning by gas inhalation was initially suspected, the attorney general's office said in a statement this week. Blood tests determined that the three Americans -- two men and a woman -- died of carbon monoxide poisoning, the office said.

Investigators discovered a failure in the apartment's gas boiler, which released a gas smell as well as carbon monoxide, a colorless and odorless gas, a spokesperson for the attorney general's office told ABC News.

One of the victims was found dead in the bathroom and is believed to have been attempting to take a shower, which could have activated the boiler, the spokesperson said.

An Airbnb spokesperson confirmed the three Americans were staying at a space listed on its platform.

"This is a terrible tragedy and our thoughts are with the families and loved ones as they face this heavy loss," an Airbnb spokesperson said in a statement to ABC News. "Our priority now is to provide support to those affected while the authorities investigate what happened and we are available to cooperate with the investigation in any way we can."

The U.S. Embassy in Mexico said it was "closely monitoring" the investigation into the deaths of three U.S. citizens in the country.

"We stand ready to provide all appropriate consular assistance," it said in a statement earlier this week. "Out of respect for the privacy of the families, we have nothing further to add at this time."

The three deaths come after another American died from carbon monoxide poisoning while staying in a vacation rental in Mexico City late last month, the victim's family told ABC San Diego station KGTV. The woman's two siblings were also hospitalized due to carbon monoxide poisoning, their family told the station.

Three American tourists who were found dead at a Bahamas resort in May also died of carbon monoxide poisoning, officials said.

The victims' families are calling for more regulation around requiring functioning carbon monoxide detectors in rental properties.

"We will fight to make sure that mandates are implemented so no other family has to deal with this type of brokenness and heartache," Marshall's mother, Jennifer Marshall, told "Good Morning America."