It happened just after 7:30 p.m. at the intersection of A and South Walnut streets in Wilmington, Delaware.
Firefighters were called to the scene for a vehicle fire. While responding, crews were alerted that children were reportedly trapped in the car.
At the scene, firefighters found the vehicle engulfed in flames.
Crews say they were told at the scene that employees of a nearby auto detailing shop had removed the two children from the burning car.
The children are 5 years old and 8 months old, authorities say.
The children's mother, who was reportedly driving, also escaped the flames.
Emergency crews say they immediately put out the fire and began to treat the injured victims.
The children both suffered extensive burns and were transported to Nemours Children's Hospital in serious condition.
The mother was transported to Christiana Trauma Center with extensive burns as well, authorities say. Her condition is unknown at this time.
No further information has been released on this incident. Police have not said what may have led to the fire.