The toddler vanished on July 8 while visiting his grandparents in the hamlet of Haut-Vernet, with police reportedly saying he may have been ‘chasing butterflies’ at the time.
Searchers played a recording of his mother’s voice from a helicopter a few days afterwards, and prosecutors later said they were considering all possibilities – including that he had been murdered, kidnapped, or run over by farm machinery.
However, there has been no trace of the little boy since.
Investigators said their latest inspection of the 1,500sqm lake, which is located beside a swimming pool in the hamlet south of Grenoble, was also fruitless.
Prosecutors said: ‘The searches are completed and have remained in vain.’
They came a week after detectives reportedly used a jackhammer to break apart a slab at a home close to where Émile’s family live.
François Balique, the mayor of Vernet, told local television news station BFMTV that gendarmes were carrying out the checks so the homeowner could finish work that was interrupted by their investigation.
Last week, Mr Balique also announced that the hamlet would remain closed to those who do not have a primary or secondary residence until the end of September.
‘I learned that despite this order, journalists were still going up,’ he said, adding: ‘I will therefore ask the gendarmes to ensure that this cannot happen.’
The initial extensive search operation to track down Émile was called off eight days after he was first reported missing.
At a news conference the previous week, public prosecutor Rémy Avon had told journalists: ‘At the moment we have no clue, no information, no element that can help us understand this disappearance.’
Last month, Mr Balique theorised that the child had been taken from the village by a nefarious character.
He told C News: ‘When we see that we have not found Emile in the town, it means that he has necessarily been moved. It cannot be otherwise.
‘[He] could only have been moved by adults, by one or more adults.
‘Either we are dealing with a madman, or we are dealing with someone Machiavellian.’
Get in touch with our news team by emailing us at [email protected].
For more stories like this, check our news page.