Further tests have now been completed by the pathologist who has given a result of carbon monoxide intoxication.
A petrol-driven pump was seized from inside the home address at the time of Zane's death and Surrey Police is conducting further inquiries to establish whether there is any liability or criminal offences in respect of the hire company who provided this equipment.
More top news
Stamp duty is to be abolished for first-time buyers on properties up to £300,000, Chancellor Philip Hammond has announced in his Budget.
The money will help pay for mental health and counselling services, regeneration in the west London neighbourhood and a new community space.
The small device was hidden in a grate in the ceiling in the only customer toilet at a Starbucks coffee shop.