The search for Ben, who went missing on the Greek island of Kos 25 years ago, is in its 17th day.
Police searches have entered a third week and a second site after it emerged Ben may have been accidentally killed by a digger driver.
The toddler from Sheffield was 21 months old when he disappeared on 24 July 1991.
Det Insp Jon Cousins, of South Yorkshire Police,  said: "The calculation is that we've lifted and sifted 800 tonnes of material.
"That's 800 hours of volunteer work - the volunteers have been turning up each and every day, one of them every single day, to help us [officers]."
"Police still seem confident they are doing the right thing."
Tom Ingall, BBC reporter in Kos said: "The search is already longer than expected and looks like it will now go through to this coming weekend too."
On Monday, Ben's mother Kerry Needham said she now believed her son is likely to be found dead.
The search has been extended to a second site 750m away from where he was last seen.
About 60 items found in the search are being sent back to the UK for analysis.
Police investigating the disappearance of Ben Needham say they have now dug up more than 800 tonnes of soil.