It is believed the kitten must have travelled in the digger’s shovel, which journeyed from a site on the M40 to Hastings on Saturday, April 23.
The kitten, and his siblings, were discovered when workers started their shift two days later.
Sadly, the little black and white kitten – who has now been named Digby – was the only one in his litter to survive.
Builder Martin Dewsnap scooped up the kitten and rushed him to the RSPCA’s Sussex East and Hastings branch, also known as Bluebell Ridge Cattery.
“The digger driver was carrying out his usual checks on the machinery when he found the three kittens,” he said.
“Sadly, two were already dead but one was alive.
“You expect to find the diesel low or something, but don’t expect to see cats inside.”
RSPCA staff were shocked when the worker arrived on their doorstep with the tiny three-day-old kitten in an ice-cream tub and asked them to help.
The centre took in the baby who was immediately fed and checked over, but the charity is still baffled as to how the litter ended up in the digger’s shovel.
Bluebell Ridge manager Myra Grove said: “It’s a mystery as to when and where the kittens started their journey and what happened to their mother, who has not been sighted.
“Digby and his siblings were very, very young so it’s not clear how they came to get inside the digger bucket.
“It’s a miracle that even one of the kittens was able to survive without his mother.
“Thankfully, a doting mother at Bluebell Ridge has now taken Digby under her wing, whilst looking after her other four kittens.
“He is now receiving the love and care he needs from new mum, Muffin, and his adopted family.”
Digby will now be cared for by staff at the Sussex centre until he is old enough to be rehomed.
Myra added: “This time of year there are a lot of unwanted kittens and most of the RSPCA centres are filled to the brim.
“We can’t emphasise enough how important neutering your pet cat is as the feline population in England escalates.
“Neutering your cat will prevent unwanted pregnancies and can also protect them from deadly diseases and infections.”
To rehome one of the RSPCA’s cats or kittens, visit http://www.rspca.org.uk/findapet.
To see all of Bluebell Ridge’s cats looking for a new home, visit http://www.bluebellridge.org.uk.
Don’t miss out on all the latest breaking news where you live.
Here are four ways you can be sure you’ll be amongst the first to know what’s going on.
1) Make our website your homepage
2) Like our Facebook page
3) Follow us on Twitter
4) Register with us by clicking on ‘sign in’ (top right corner). You can then receive our daily newsletter AND add your point of view to stories that you read here.
And do share with your family and friends - so they don’t miss out!
Always the first with your local news.
Be part of it.