The parents of toddler Julen Rosello, who reportedly lost another young son in 2017, have said the family had no doubt that the boy fell into the borehole after walking away from his parents, who were preparing a countryside lunch Sunday near Totalan, a town northeast of Malaga.
Adults can't enter the waterhole, which has a diameter narrower than 25 centimeters (10 inches).
Emergency teams said the hair samples of the boy, extracted from soil inside the shaft, suggested the toddler may be trapped inside but at a deeper section than machinery and surveillance equipment have so far been able to reach.
The government's representative in the Malaga province, Maria Gamez, said the boy's hair samples gave rescuers "scientific evidence that the minor is there."
She also said that workers were still flattening areas near the borehole to allow heavy boring machinery to dig a side tunnel to reach the shaft.
Emergency workers have been unable to pass through the 73-meter mark of the shaft, blocked by an accumulation of hardened soil and rocks. They expect to be able to reach the deepest part of the shaft from the side tunnel in "24 to 48 hours."
Jose Rosello, Julen's father, that he and his wife were "heartbroken" by the long wait.
"It feels like we have been waiting for months," he told a scrum of reporters on Wednesday. "We are not going to give up ... We have the hope that an angel is going to show up for my son to come out alive."
Spanish media have reported that the couple, who lives in a coastal suburb near Malaga, lost another son in 2017. Julen's elder brother, Oliver, was 3 when he suffered a heart attack during a family walk on their local beach.
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