The families of some Muslim youth, detained in connection with the twin blasts, on Sunday alleged police harassment in the name of investigations and threatened to launch an agitation if they were not released immediately.
City-based civil rights activists claimed that over 40 young men had been picked up since the August 25 blasts that claimed 43 lives, but none of them was produced in the court.
The family members, who included daily-wage earners, told reporters that their dear ones were picked up by plain-clothes policemen without giving any reasons and their fate was not known.
"My younger son was taken away by the police from my house on Thursday. As a precaution, I had sent my elder son with him. Both of them have not returned so far. Please return my sons," Mujeebunnisa, an elderly widow, said.
Zaheda Begum, mother of Rayees Ahmad, said her son was taken away by two policemen when he was returning home from work in Secunderabad.
Ghousia Begum, mother of auto-driver Abdul Raheem, said her son was dragged from home by the police on Monday night.
"I am a heart patient and I do not have the money even for my medicine. Where should we go for justice?" she asked. Secretary of Civil Liberties Monitoring Committee Lateef Mohammed Khan released a list of 21 persons who, he alleged, were picked up by the police illegally. He claimed that they were kept at illegal detention centers.
He demanded that the investigations into the blasts be conducted in a transparent manner as people had a right to know about the culprits. He threatened to launch an agitation if the demands were not met.
Meanwhile, city police commissioner Balwinder Singh assured a delegation of Muslim leaders that police would soon come out with details of those arrested during the last few days.