(KTLA) – Two Americans vacationing in Mexico were found dead in their hotel room 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 the village of 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 San Lucas.

The couple’s cause of death was listed as “intoxication by substance to be determined,” the AG’s office said.

In a GoFundMe post, a friend of Lutz suggested 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, the organizer of the online fundraiser, wrote. “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, a resident of Newport Beach, was the founder of LES Labs, a nutritional supplement company. Lutz, originally from Salt Lake City, Utah, worked as a nanny, according to her Facebook page.

“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,” the hotel’s manager said in a statement to PEOPLE. “We are truly heartbroken by this terrible tragedy. Our hearts are with the impacted families and loved ones during this unimaginable loss.”