It was the most heartbreaking tragedy of the floods that wreaked havoc around Britain last year. Little Zane Gbangbola died at home – in the middle of the night – after being poisoned by gas. For months after his death, police and other official agencies ruled out fears that the deadly fumes had come from a nearby landfill site. Instead, they insisted carbon monoxide from a faulty pump hired by his family had caused his death. But now The Mail on Sunday can reveal the damning evidence that proves the authorities have known for 14 months that hydrogen cyanide gas capable of killing Zane had leaked into the family's home as it was engulfed by floodwater. Scroll down for video . Little Zane Gbangbola (pictured) died at home – in the middle of the night – after being poisoned by gas which authorities claimed was from a faulty pump at his house . But damning new evidence proves the authorities knew for 14 months that hydrogen cyanide gas capable of killing Zane had leaked into the family's home (pictured) as it was engulfed by floodwater . The leaked official records reveal for the first time: . Last night, claims of a cover-up over Zane's death by police, the Environment Agency, Public Health England and local authorities intensified when the documents uncovered by the MoS also revealed no traces of carbon monoxide had been detected at the home in Chertsey, Surrey. The witness statements, marked restricted and confidential, were provided to police by senior fire officers the day after they attended the scene of the tragedy on February 8 last year. But Zane's grieving parents Kye and Nicole Gbangbola have faced a 'wall of silence', leading to claims of a cover-up while public agencies repeatedly insisted the boy died from carbon monoxide poisoning and that there was no risk to the wider public. Local residents accused the authorities of lying and putting lives at risk. The Gbangbolas' neighbour, Paul Marsden, 53, said last night: 'It is a disgrace that the authorities have not warned people about the dangers lurking in this land near our homes. Dr Ivan Vince, an expert in landfill gases, said last night that it was possible the cyanide gas had leached from a nearby landfill site (pictured) 'They are hoping it will go away – but it won't. It should not have taken the loss of a young life for this to come to light. Continuing to lie to people about what is there is putting other lives at risk. 'We have said all along that they found hydrogen cyanide at Kye and Nicole's house and here is the proof.' Just hours after the tragedy, despite the fact that police were in constant communication with fire chiefs, Surrey Police Chief Superintendent Dave Miller declared that landfill gases were 'not one of our lines of inquiry' into Zane's death. The force spent the next 11 months investigating carbon monoxide poisoning as the cause, before dropping its case in January on advice from the Crown Prosecution Service that there was no case to answer in relation to a hired petrol-powered pump in the family's home which they insist was never switched on. Nicole and Kye Gbangbola also needed hospital treatment because of hydrogen cyanide exposure on the night of their son's death. For months after his death, police and other official agencies ruled out fears that the deadly fumes had come from a nearby landfill site . Kye, 48, has been permanently paralysed from the waist down because of the gas, which was used to murder millions in the Nazi death camps. The couple have struggled for answers from the police, Environment Agency, Public Health England and councils ever since – and are still waiting for a coroner's inquest to be held because of the delays caused by the long-running police investigation. The Mail on Sunday has led the way in covering the tragic case – but has been stonewalled at every turn. Now this newspaper has seen leaked statements from police interviews with senior firefighters who were among the first of dozens of emergency personnel on the scene when Zane was rushed to hospital. The highly experienced officers serve with Surrey Fire and Rescue Service's Detection Identification and Monitoring team, which is called in to investigate gases. A commanding officer's statement to police says: 'As we were about to leave the premises, one of the gas detectors went into an amber alarm indicating hydrogen cyanide had been detected at levels of ten parts per million. We left immediately.' The officer says the level of gas in the house is considered dangerous if inhaled for more than 15 minutes. An immediately fatal concentration is 50 parts per million. Fire crews fled the riverside home in Chertsey, Surrey (pictured) for their own safety after their specialist gas detectors sounded the alarm for dangerous levels of hydrogen cyanide . The reading was taken at 7.29am – four hours after Zane's mother found him unconscious in a bedroom above the hallway and rang 999. After Zane was found, emergency services had opened doors and windows to ventilate the property for several hours. The firefighters double-checked their equipment and re-entered the house on two more occasions to confirm that hydrogen cyanide was in the property at 'concentrated levels', according to their incident log. It records the gas being detected at 7.47am and 8.19am. Neighbour Mr Marsden recalled seeing the firefighters 'ducking in and out of the house in breathing apparatus.' He said: 'The fire chief said to me there was hydrogen cyanide. I asked if it was ground gases and he said that was right and everyone will have to go to hospital.' Another statement seen by this newspaper says the gas detectors used by the fire service had been tested and certified as working correctly four days before Zane's death. The Gbangbolas said last night that they could not comment on the fire service documents for legal reasons ahead of Zane's inquest, due to be held later this year. A close family friend said: 'The truth is out – they have been gassed. Kye and Nicole are very angry.' Dr Ivan Vince, an expert in landfill gases, said last night that it was possible the cyanide gas had leached from the landfill site. He added: 'If this was an old unregulated tip, it could well be that cyanides were dumped many years ago. If there is acid spilt at the site, and then the water came out due to the flooding, then that would bring acid to the cyanide and release hydrogen cyanide.' This newspaper asked Surrey Police why the force had not disclosed that it knew hydrogen cyanide had been detected in the family's home hours after Zane had died. We also asked why the force spent 11 months investigating the carbon monoxide theory. A spokesman did not answer those questions but said in a statement: 'In February 2014, the post mortem examination into Zane's death proved inconclusive. 'Further thorough and extensive tests were completed. The pathologist gave a result of carbon monoxide intoxication.' The police, Environment Agency, Public Health England, Surrey Fire Service, Surrey County Council and Spelthorne Borough Council all said they could not comment in detail ahead of the coroner's inquest. A spokeswoman for Spelthorne council said: 'We are aware it is the family's belief that there is a link between the landfill close to their home and the tragic death of their son. 'However, based on current information, we do not believe there is any evidence of a causal link.'
Zane Gbangbola died at home in the middle of the night after gas poisoning .
Authorities denied that deadly fumes were coming from nearby landfill site .
They insisted carbon monoxide from faulty pump in house caused his death .
Evidence shows authorities knew hydrogen cyanide leaked into family home .
Fire crews fled the riverside home for their own safety after their specialist gas detectors sounded the alarm for dangerous levels of hydrogen cyanide four hours after Zane was discovered by his mother.
The concentration of the gas found could be fatal within 15 minutes; .
Carbon monoxide was never detected in the family's home; .
Neighbours were evacuated amid fears of 'contamination from floodwater'; .
Police and other agencies were fully informed of hydrogen cyanide at the property at the time, but never confirmed it publicly despite repeated questioning by this newspaper.