The mother of Ben Needham said signs of blood found on a toy car and sandal which are believed to have belonged to the toddler point towards "a cover up."
Sheffield-born Ben was 21 months old when he went missing in 1991 while playing near a farmhouse on the Greek island of Kos, which was being renovated by his grandfather.
South Yorkshire Police formally ended a search on the island last October, saying they believe Ben died as a result of an accident involving a digger.
Det Insp Jon Cousins said the development "corroborates and strengthens" the theory Ben died in an accident near to where he disappeared.
However, the sandal was found earlier in 2012, while the toy car was discovered in 2016 at another spot.
Kerry Needham is now convinced her child was taken from the site where he was buried before British police returned to carry out a dig there last year.
"It shows more of a conspiracy because they didn't find Ben's body," Kerry told ITV's Good Morning Britain. "That proves it to me without doubt they obviously moved him and buried him and for whatever reason dug him up. There's no other explanation. It's all been a massive cover-up.
"This confirms what the police have been saying all along. My Ben was killed in an accident. But it also suggests that not only did they kill my boy and bury him where the toy car was found, they then moved him before police got to the site last October.
"What kind of human being does that? It just infuriates me. How can they do such a thing? He was definitely wearing those sandals that day. They were the only ones we could keep on his feet."