The mum of Ben Needham said she fears her son's remains will be found buried under rubble a police search team has started examining.
Kerry Needham, aged 43, said detectives believe Ben was accidentally killed and his body hidden.
They are working on the theory that he was crushed by a digger working close to where Ben was playing when he went missing on the Greek island of Kos in July 1991.
The 21-month-old was outside a farmhouse his grandfather was renovating when he vanished.
Police officers are still excavating the land around the farmhouse to look for remains but have now moved to a second site, where rubble from the farmhouse area was dumped around the time Ben vanished.
Kerry told the Daily Mirror: “I’m terrified he is there. These next few days are going to be agonising.
"The thought of him being buried under all that is sickening. I thought it was impossible to hurt more – but every day this gets more painful and traumatic.
“I think the police are right. There was an accident and his body was taken and may have been hidden elsewhere.
"Seeing this new site has made it even more real – the fact the police are convinced he’s dead."
The digger driver suspected of accidentally crushing Ben died last year.
A friend came forward over the summer to suggest the theory.
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