How many people are said to be injured in the accident altogether? [originaltext

A woman in her 40s was severely injured and three children aged between 6 and 11 were hurt when a "fireball" engulfed a portable gas barbecue. Fire and ambulance crews were called to a playing field in Stopsley Way, Luton, at about 16: 30 British Summer Time.
    The badly burned woman was airlifted to the specialist burns unit at Broomfield Hospital in Chelmsford. The children sustained 15% to 20% burns to their upper limbs and three other adults suffered minor burns. The East of England Ambulance Service said the children were all taken to Luton and Dunstable Hospital and the three adults were taken to the lister Hospital in Stevenage.
    Bedfordshire Fire and Rescue Service said a group of about 20 people were thought to have been at the playing fields when the barbecue, caught fire. The cause of the blaze was not yet clear but would be the subject of a fire service investigation, the spokesman added.