A Texas woman and her 8-year-old daughter died of carbon dioxide poisoning after leaving the car running in the garage in a bid to stay warm amid record-low temperatures and a power outage.

The same incident also sent a man and a 7-year-old boy to the hospital, making them part of more than 300 cases of carbon monoxide poisoning reported in the last few days.

Houston Police Department and Houston Fire Department officers were dispatched to 8300 La Roche for a welfare check, but instead found four people “affected by carbon monoxide poisoning.”

“Initial indications are that [a] car was running in the attached garage to create heat as the power is out,” the statement reads.

“Cars, grills and generators should not be used in or near a building.”

Police say that they found the woman dead in her vehicle, while the girl was found dead in the condo, which is attached to the garage that housed the running car.

The woman was on the phone with a relative in Colorado when she felt disoriented and passed out, prompting her relative to call HPD.

“It’s a very difficult time. A lot of people are without power,” said Lt. Larry Crowson.

“I know it’s cold, but you’ve got to be careful about using generators or cars inside a garage, or any type of fire, grill or charcoal grill.”

The unfortunate incident comes after more than 1 million people lost power in the Houston area as demand for electricity soared during the coldest night in 32 years.

Often called the “silent or invisible killer,” Carbon monoxide is an odorless, colorless gas that can quickly cause disorientation, sudden illness or even death.

According to the Centers for Disease Control and Prevention, it is found in fumes produced any time fuel is burned in cars, engines, stoves, lanterns, grills, fireplaces, gas ranges or furnaces.