Julen Rosello, who is two, fell down a very narrow shaft more than 100 metres (330 feet) deep on Sunday while playing as his parents had lunch nearby in the town of Totalan near Malaga, family members said.
Rescuers are unable to get to where they believe the child is as a layer of earth, sand and stones believed to have been dragged down by Julen when he fell have blocked the well.
The toddler is believed to be underneath and the discovery of several strands of his hair by rescuers appears to confirm that theory.
As such, they are digging two tunnels, one parallel to the well and another at an angle aiming to reach Julen.
But the work is complicated by the state of the soil.
Engineer Juan Lopez told reporters that the vertical tunnel was progressing “for the moment without too many problems.”
But the horizontal one is causing “problems,” he added. Excavating that tunnel “within less than two days is really complicated,” he said.
This race-against-time recalls several other high-profile cases in the 1980s.
Alfredo Rampi, an Italian boy, was found dead in a well near Rome in 1981 while Jessica McClure, an 18-month-old girl, was rescued alive from a well in Texas in October 1987 after more than two days inside.