A bomb exploded inside the outer boundary of Jessore Central Jail on Wednesday leaving a garbage collector (tokai) wounded.
UNB said the victim was identified as Jahidul Biswas alias Kalu, 40, who used to collect garbage pulling his three-wheeler.
The injured person said he found a white plastic pot near the staff quarters of the jail in the afternoon.
As he hit a coconut tree with the pot, it suddenly went off with a big bang, wounding his right hand severely, he said.
Asked, jailer Abu Taleb said though jail is a restricted area for others, Kalu normally comes inside the outer boundary for collecting waste and plastic materials as his father was a prison guard.
"We don't understand how the bomb came inside the jail. Police are seriously investigating the matter," he added.
Later, Kalu was admitted to the Sadar Hospital.