The Delta Police Department said just before 9 a.m. PT Saturday that it was engaged in an urgent ground and air search for the woman.
She was last seen at around 3 a.m., running from the burning motorhome in the 10200 block of River Road.
"A passing motorist saw the woman fleeing the motorhome and she appeared to have severe burn injuries to her face," Delta police said in a written statement. "At the time, she was wearing pyjama bottoms and a light-coloured tank top."
Police are extremely concerned about her condition, and are asking anyone who may have seen her to call 911.
Officers have not yet been able to speak with the two burn victims in hospital.
Google Map: 10200 block River Road