A Newport Beach business owner and his girlfriend were found dead at a resort near Cabo San Lucas on Tuesday under circumstances that remain under investigation.

The bodies of John Heathco, 41, and Abby Lutz, 28, were discovered inside a room at the upscale Hotel Rancho Pescadero in El Pescadero around 9 p.m. Tuesday, the Baja California Sur Attorney General’s Office confirmed to ABC News.

El Pescadero is located on the Pacific coast of the Baja Peninsula roughly one hour north of Cabo.

Their cause of death was listed as “intoxication by substance to be determined,” the AG’s office told ABC News. In a GoFundMe post, a friend of Lutz says the couple may have suffered carbon monoxide poisoning.

“Abby and her boyfriend thought they had food poisoning and went to the hospital to get treatment. We were told they were feeling much better a few days later,” Gabrielle Slate, who organized the fundraiser, posted. “We received a phone call saying that they had passed away peacefully in their hotel room in their sleep. We have been told it was due to improper venting of the resort.”

According to his LinkedIn profile, Heathco founded LES Labs, a nutritional supplement company based in Newport Beach.

Abby Lutz, who was from Utah, was working as a nanny.

“Abby was the most beautiful soul and we will miss her so much,” Slate said.

Proceeds from the GoFundMe will help cover transportation and funeral costs.

In a statement Thursday, the resort expressed condolence but offered few details.

“We are truly heartbroken by this terrible tragedy. Our hearts are with the impacted families and loved ones during this unimaginable loss,” the hotel’s manager told NewsNation. “Local authorities have not confirmed with the hotel the cause of death … We can confirm there was no evidence of violence related to this situation, and we are not aware of any threat to guests’ safety or wellbeing.”

In October, three Americans who were staying at an Airbnb in Mexico City died of carbon monoxide poisoning, authorities said.