Tahoe City, CA – Actress Anna Faris is thanking first responders after she and her family members were “saved from carbon monoxide” while vacationing over the Thanksgiving holiday.

According to the North Tahoe Fire Protection District in Tahoe City, California, a family of 13 “all fell ill to varying degrees” after arriving at a rental home on Lake Tahoe last week. The family initially attributed their symptoms to altitude sickness, and two of them sought medical treatment.

Staff at a local hospital determined that they were suffering from carbon monoxide poisoning. First responders were dispatched to the rental home to check on the 11 family members who were still there. They determined that the home, which did not have carbon monoxide alarms, had nearly six times the maximum recommended indoor carbon monoxide levels.

Two additional members of the family were taken to the hospital, and the remaining nine received medical treatment at the home.

Fire officials did not identify the family involved, but Faris later took to Twitter to thank the local first responders after her family was “saved from carbon monoxide.” She said she was “not quite sure how to express gratitude to the north Lake Tahoe fire department.”

It’s not clear if Faris was among the four who were hospitalized. Fire officials did not specify exactly how the dangerous amount of carbon monoxide built up in the home but said the family is “lucky to be alive.”

Carbon monoxide is an odorless, invisible gas that can suffocate victims by depriving the bloodstream of oxygen. Symptoms of carbon monoxide poisoning include headache, dizziness, disorientation, nausea, loss of coordination and difficulty breathing.

In a news release, North Tahoe Fire Protection District Fire Chief Mike Schwartz encouraged travelers to make sure their accommodations are equipped with working smoke and carbon monoxide alarms. He suggested that travelers “consider bringing your own alarm when you travel, just to be safe.”