A 3-month-old baby died in Houston this week after being left alone inside a hot car, officials said. The exact circumstances surrounding the incident are under investigation and the infant’s cause of death is still being determined by the medical examiner’s office, according to the Houston Police Department.

Authorities were called to a Houston address just before 3:30 p.m. on Tuesday, where they found a 3-month-old boy unresponsive, Houston Police Assistant Chief Yasar Bashir said at a news conference. The infant was pronounced dead at a local hospital.

“We learned, very sadly, that the child was left unattended in a vehicle,” Bashir told reporters.

He could not say how long the infant was inside the car or whether any of its windows were rolled down during that time. The infant was originally found by the mother, who was not identified by name. Bashir said the mother “was visiting” but did not provide more information.

The incident reportedly happened outside a Houston mental health clinic, where the infant’s mother was inside with a 4-year-old child, CBS affiliate KHOU 11 reported. The mother reportedly entered the clinic some time after 12 p.m., according to the station.

Homicide detectives with the Houston Police Department are involved in the investigation. While Bashir spoke at the news conference, he said detectives had returned from the hospital to the scene of the investigation to interview witnesses. The infant’s mother and father, who was not there when the baby was found, were both at the scene by then and cooperating with authorities, according to Bashir. The mother was accompanied by a 4-year-old child, he said.

“I give my condolences to the parents, the mom and dad, and I also want to thank the staff here and the nurses, HFD who provided CPR and did everything they could to save this child,” Bashir said.

Bashir said any potential charges depend on what the autopsy report and probe reveal. But the assistant chief called the infant’s death “avoidable” and reiterated how dangerous it is to leave a child unattended inside a vehicle, especially in Houston’s summer heat.

“Houston gets very hot, and under no circumstances you should leave a child in the car. Not even for a moment,” Bashir said.

“From time to time, we have incidents like this, which should never happen. Especially during the summertime,” he continued. “You should never leave a child unattended, and there should be zero child infant deaths in the city. In my opinion, that’s avoidable.”

About 40 children die each year in the U.S. from heatstroke after being left or becoming trapped in a car, according to the National Highway Traffic Safety Administration. That breaks down to about one death every 10 days.

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