Murshidabad district, triggering protests by locals, officials said on Saturday.
Police had to fire tear gas shells to disperse the agitators, they said.
The labourer was taken into custody on Wednesday in connection with a theft at a policeman's house.
The father of the deceased has alleged that his son was beaten to death in custody on Friday evening, a charge denied by the police.
"My son was innocent. He was picked up by the police on Wednesday, and they killed him in custody,” he claimed.
A senior police officer at Nabagram Police Station said the accused was neither beaten up nor was he in lock-up.
"He was being questioned at a spot behind the police station, where we found him dead around 8 pm on Friday," the officer said.
Police have registered a case of unnatural death and are investigating the matter.
“The body of the deceased will be sent for post-mortem examination. We will also check CCTV footage for more details,” he added.
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