(NewsNation) — Paramedics who entered the Mexican resort hotel where an American couple was mysteriously found dead have said they also got sick after entering the room.

The bodies of John Heathco, 41, and Abby Lutz, 28, were discovered inside a room at the upscale Hotel Rancho Pescadero in the village of El Pescadero on June 13.

Family members have suggested they may have died from carbon monoxide position, but an official cause of death has not yet been determined.

The two paramedics, siblings Grisel Sotelo and Fernando Sotelo, were the first to respond to the hotel room. Once inside, they were overcome by an unknown substance, and barely made it back to their ambulance to administer oxygen, according to a GoFund Me campaign for them.

They remain hospitalized with breathing problems.

Mexican authorities have said Heatcho and Lutz’s deaths were caused by “intoxication of an unknown substance.”

The hotel’s general manager called the deaths a “terrible tragedy,” adding, “We understand authorities immediately tested the air quality in the room after responding to the situation, and at the time, did not report any findings of gas or carbon monoxide and advised that the hotel was cleared to continue normal operations. The hotel continues to monitor air quality.”

It is not known whether the detectors were working in the couple’s room, but a number of current and former employees have reportedly claimed gas detectors were regularly deactivated at the hotel because guests kept complaining about them going off.

The hotel has not responded to the claims about deactivated detectors.

Days before their deaths, the California couple had been hospitalized for suspected food poisoning.
Medical experts have said that could be a tell-tale sign.

“It is possible that somebody had carbon monoxide poisoning and was evaluated and diagnosed with something else because the symptoms are so non-specific,” said Dr. Evelyn Huang, an emergency room doctor at Northwestern Memorial Hospital.

She added, “Carbon monoxide does not have a smell. Often, people don’t know that they’re breathing it in. It’s possible that you know if they were breathing those levels in for a short amount of time that could prove deadly.”

There have been multiple tourist deaths at Mexican resorts in recent years that have been linked to carbon monoxide poisoning.