An investigation is underway as to what caused a fire that left a woman trapped in her unit in north Barrie. Barrie Fire and Emergency Services tell CTV News that a call for a residential fire came in at 11 p.m. Sunday night. Six apparatus attended the Duckworth Street fire and discovered a woman who was trapped in her apartment. Fire services say the fire had originated in her unit. The woman was trapped in her bedroom and heavy smoke prevented her from being able to leave the room or put the fire out. According to Barrie Fire, firefighters had to talk to the woman through an open window. Because of where the fire was, emergency crews had to put out the blaze before they could reach her. The woman was transported to hospital with smoke inhalation, but no other injures were reported. Barrie Fire Services says the fire had spread inside and damage to her unit was extensive but there was no apparent damage to other nearby apartments. Fire crews battled the blaze until just after 2 a.m. Monday. The fire forced several residents out of their apartments, many of them took temporary shelter in Barrie Transit buses that were called to the scene. The cause of the fire is now being investigated by Barrie Fire Investigators who returned to the scene on Monday morning.