A 12-year-old boy seriously injured in a crash on Thursday remains in the hospital.

His mom was killed in a one vehicle accident in Willacy County. DPS says 30-year-old Sandra Diaz and her three children were not wearing seatbelts at the time of the accident.

Her two daughters were treated and released from the hospital.

Her son's condition was upgraded Thursday's afternoon to critical but stable condition.    

DPS says speed and weather conditions were both factors in the accident.