NEMMA 76-year-old man has been arrested on suspicion of administering poison after children fell ill at a summer camp in Leicestershire.
Police said an investigation was under way in Canal Lane, Stathern, after eight children were taken to hospital as a precaution on Sunday. All have since been discharged.
Officers had gone to the camp with East Midlands Ambulance Service after receiving reports about the children feeling unwell.
The arrested man was detained on suspicion of administering poison/a noxious thing with intent to injure/aggrieve/annoy. He remains in custody.
Leicestershire Police said the investigation was now being led by the East Midlands Special Operations Unit's major incident team.
"This is to allow a full and thorough investigation to take place with dedicated resources," a spokesperson said.
Officers remained in Stathern on Thursday, carrying out further inquiries and providing reassurance to families affected.
The police watchdog has confirmed it is looking into the force's handling of the incident.
An Independent Office for Police Conduct (IOPC) spokesperson said it received a "conduct referral" on Tuesday from the force "relating to their handling of concerns passed to them over the wellbeing of a group of children".
"Our assessment team has examined all available evidence and concluded the matter should be independently investigated by the IOPC," they said.
"The investigation will look at whether there were any breaches of professional behaviour - namely a failure to carry out duties and responsibilities - that resulted in a delay in Leicestershire Police's response to what was later declared a critical incident."
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