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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Paramedics were on standby outside the police cordon as armed officers stood by the property.
A team of researchers has taken samples from the ten busiest London Underground lines to work out which are the dirtiest.
The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.