Three American tourists were found dead last week in a Mexico City apartment they were renting after apparent carbon monoxide poisoning, Mexican authorities confirmed to Reuters on Wednesday.

Friends Kandace Florence, Jordan Marshall and Courtez Hall were visiting the Mexican capital to celebrate the Day of the Dead holiday, according to U.S. news site WAVY, based in Virginia Beach, Virginia, where Florence and Marshall were from.

The Mexico City Attorney General's office, which opened an investigation into the deaths, said the victims' bodies were found Oct. 30 and that studies indicated they died of carbon monoxide poisoning.

The victims were staying in La Rosita, a neighborhood in the Mexico City borough of Cuajimalpa and close to the upscale Santa Fe business district.

Airbnb did not immediately respond to a request for comment, but in a comment to Bloomberg said the deaths were a "terrible tragedy" and that the company was ready to assist with inquiries from authorities.

The tragedy comes as an influx of Americans and other foreigners visit and move to Mexico.

Last month, Mexico City's government signed an agreement with the short-term rental site in what Mayor Claudia Sheinbaum described as an effort to boost the number of "digital nomads" coming to Mexico City.

Gas leaks have caused other deadly incidents involving tourists in Mexico.

In March, an explosion caused by a gas leak killed two people and left 18 injured in a restaurant in a beachside tourist town of Playa del Carmen.

In 2018, a family of four from Iowa was found dead at their vacation condominium in Akumal, about an hour from Cancun, suffocated from gas.

The U.S. embassy in Mexico City did not immediately respond to a request for comment.