With no electricity in their home for hours, the Houston family tried to fight off the freezing cold by running their car in the attached garage, authorities say.

When Houston police officers entered the property to conduct a welfare check, they found the two adults and two children, police said in a statement Tuesday morning.

The woman and girl did not survive, and the man and boy were taken to a hospital.

The deaths are among a rising number of reports of people being poisoned by carbon monoxide as Texans face a deadly winter storm that has brought record-low temperatures and demands for electricity that overwhelmed the state’s grid, leaving more than 3.2 million people in the dark and with no heat for more than 24 hours.

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As more reports of poisoning emerged Tuesday, government officials sounded the alarm.

“SPREAD THE WORD: The number of people being admitted to local hospitals for carbon monoxide is rising at a disturbing rate. Do not bring any outdoor appliances (grills, etc) inside, or run your car inside the garage,” Harris County Judge Lina Hidalgo wrote on Twitter.

In a video from the Emergency Operations Center, Hidalgo said the county had received reports of at least 50 incidents of CO poisoning, calling it the second-biggest challenge the county faces after the widespread power outages that have left 1.37 million people in the Houston region with no power, a situation she described as “a nightmare.”

The Cy-Fair Fire Department, which provides emergency services to the Cypress-Fairbanks area outside Houston in Harris County, reported Tuesday afternoon that it had been receiving calls about carbon monoxide poisoning and that at least 23 people, including 12 children, in several incidents were taken to hospitals with CO poisoning in the previous 24 hours.

All of the incidents had resulted from people using charcoal grills to heat their homes in the freezing conditions, the department said, issuing a stark warning against the use of ovens, grills and generators indoors.

“Carbon monoxide is an odorless and colorless gas that can kill you,” the department said on Twitter.

On Monday night, the department responded to a call about a family of six, including four children, that had used a charcoal grill for about four hours to fight off the freezing temperatures. When emergency personnel arrived at the home, the apartment was filled with smoke, the department reported.

“We are in a super dire situation. With power outages, no water and historic low temperatures, people are desperately trying to keep their loved ones warm,” said Daniel Arizpe, public information officer at the Cy-Fair Fire Department.

The department’s concern is that with the forecast for Tuesday night indicating below-freezing conditions and more ice and snow expected, power outages are likely to continue, leaving people even more desperate and leading to more cases of CO poisoning, Arizpe said.

“Nobody was prepared for this prolonged, hard freeze and snow and ice and the power cuts that goes with it. This is a grim situation, and everyone is just trying to do their best,” Arizpe said, adding that Texans are not used to dealing with such extreme cold. Many of them might not have been aware of the risk of CO poisoning.

Emergency crews are overwhelmed and in disaster mode, Arizpe added. The responders are scrambling to handle the deluge of 911 calls, most of them related to carbon monoxide detection, house fires or health emergencies involving people dependent on oxygen or electrically powered ventilators, he said.

“This is essentially like Hurricane Harvey, without enough hands,” he said.

At least 300 cases of poisoning were reported in Harris County alone since the beginning of the storm, including 90 calls to the Houston Fire Department and 100 cases treated in emergency rooms, the Houston Chronicle reported.

The Houston Police Department did not immediately respond to several requests for comment.

The Cy-Fair Fire Department is encouraging people to avoid using open-flame heaters indoors and to use other approaches such as staying in centrally located closets, which are likely to be the warmest spots in their homes.

Concerns also grew among emergency responders about the storm’s potential toll on the most vulnerable, including the homeless and the elderly.

“We are asking people to check in on their neighbors, on their friends, as we try to keep up with their calls and help everyone we can,” Arizpe said.

In preparation for the storm, Houston set up a shelter and warming center at the George R. Brown Convention Center for homeless people. By Tuesday morning, the shelter was full and taking no one else.

At least one homeless person, a 60-year-old man, was found dead “possible from exposure,” the Harris County Sheriff’s Office said.