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.
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Police are investigating whether a Land Rover Defender found burnt out in West Horsley was involved in Tuesday night's ram raid.
The work, called Gift Horse, replaces the giant blue cockerel that previously sat on the plinth.
50 of the country's worst pollution blackspots are in the capital. Many in places you may visit every day.