Potrero, CA – One person died and two others were sickened in a suspected carbon monoxide poisoning at a home in southeast San Diego County Wednesday, officials said.

San Diego County Sheriff’s Department Lt. Karla Menzies said the victims were found by authorities at around 9:15 a.m. at a home on Hartley Hill Road in Potrero, a rural community in the Mountain Empire area of southeast San Diego approximately 40 miles from downtown San Diego.

One person had died at the scene; the other two victims were taken to Sharp Grossmont Hospital in La Mesa where they are expected to recover.

Cal Fire Capt. Isaac Sanchez said firefighters launched an investigation at the scene and believe the victims may have been exposed to carbon monoxide, also known as CO. Sanchez said crews ran a test inside the home and found elevated levels of CO inside.

Sanchez said the person who died was a woman; the two others were a man and a child. The San Diego County Medical Examiner’s Office will perform an autopsy on the woman and determine her cause and manner of death.

According to the Centers for Disease Control and Prevention, carbon monoxide is an odorless, colorless gas that can be deadly.

It is found in fumes produced by burning fuel in cars, small engines, stoves, lanterns, grills, fireplaces, gas ranges, or furnaces. The CDC says it can “build up indoors and poison people and animals who breathe it.”

The CDC says symptoms of CO poisoning can feel “flu-like” and include headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. Those who are sleeping can die from CO poisoning before experiencing symptoms.

According to the CDC, more than 400 Americans die each year from unintentional CO poisoning not linked to fires, while more than 4,000 are hospitalized.