Thai Ly Hao Nam died after 100 hours of unsuccessful attempts by different agencies to save him, deputy chairman of the province Doan Tan Buu told reporters.
A team medical and forensics experts and local authorities concluded that the boy had died based on various factors including the location of the accident, the depth of the pillar, the length of rescue attempts, and possible injuries, he said.
The plan is now to recover his body as soon as possible, he added.
The 35-meter concrete pillar remains underground. Attempts to pull up the pillar have yet to succeed.
Nam and three of his neighbors went to a bridge construction site on Provincial Road 857 in Phu Loi Commune to gather pieces of iron.
Nam was walking when he fell into the hollow concrete pillar, which measures 25 centimeters across, and has been trapped.
No one knows for sure where in the pillar the boy is. Witnesses said he screamed for help for 10 minutes after falling in, but rescuers have not heard from him.
Le Hoang Bao, director of the Dong Thap Department of Transport, said the construction site is fenced and there are warning signs, but officials would check for possible safety violations.