The boy fell into the borewell at around 5.30 p.m. on Friday and got stuck at 30 feet. Late at night, he fell further down to about 100 feet.
Speaking to reporters, Tamil Nadu Health Minister C. Vijaya Baskar said: "The rig deployed to dig a hole near the borewell has gone to a depth of only about 40-ft owing to the rocky terrain."
He said the next course of action will be taken after discussions with different organisations.
The plan is to dig about 90 ft hole near the borewell, send firemen into the new hole and reach out to the boy after burrowing a tunnel inside.
According to reports, stronger blades that can break rocks are being sent from Chennai to be fitted in the rig.
On Saturday, the National Disaster Response Force (NDRF) and State Disaster Response Force (SDRF) took over the rescue operation as other techniques used to take the boy out of the borewell failed.
Initially, Earthmoving equipment was pressed into service to dig a pit near the borewell to reach to the boy. But, it was stopped midway as the terrain was rocky. And, it was felt that this process could cause vibrations that may loosen the soil inside the borewell, thereby slipping the boy further down.
Later, the rescue team used a special equipment 'borewell robot'. But that too was not successful.
Several teams with their own technologies have tried in rescuing the boy, but all have so far, unfortunately, failed.
( With inputs from IANS )