No decision has yet been taken on whether to prosecute a man from Berinsfield for possessing a dangerous chemical.
Twenty-six people, including 18 firefighters and four ambulance staff, attended Oxford's John Radcliffe hospital for check-ups on June 13 after David Brind's shed in Ock Drive caught fire.
Water from hoses created a poisonous gas when it came into contact with the aluminium phosphide pellets he kept for killing moles.
Although the incident happened more than two months ago, the authorities have still not decided whether to press charges. South Oxfordshire District Council's assistant head of environmental health Jon Payne said he was waiting for the Health and Safety Executive's decision.
Tony Mitchell, of the HSE, based at Stoneleigh, near Coventry, said: "The investigation is continuing and should take a further two weeks."
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