Police have been questioning family members of five attackers who stormed an upmarket restaurant in Bangladesh, killing police officers and hostages.
The incident in Dhaka's diplomatic zone over the weekend resulted in the five attackers being fatally shot by security forces, a police officer said.
The officer said parents and relatives of the five men were questioned on yesterday and some again today.
The officer also said authorities have freed three of five former hostages they had been holding for questioning. Authorities were looking into the backgrounds of these people and questioning their families and friends.
Police have eight people in custody, including one described as an attacker, but no one has been arrested as a suspect.
Two police officers and 20 hostages - nine Italians, seven Japanese, an Indian and three students at American universities - were killed.
Thirteen hostages were rescued when security forces stormed the restaurant on Saturday morning. Authorities said security forces, civilians and some hostages were injured.
Meanwhile, Imtiaz Khan Babul, a politician in the ruling Awami League party whose son Rohan Imtiaz was one of the Bangladeshi attackers, said many other young Bangladeshi men have been missing like his son was for several months before carrying out the attack.
Mr Babul said the missing men are from educated families and are sons of serving and retired government employees.
He urged the government to take these cases seriously and give them importance.
"Those who have recruited them have done it with a target," said Mr Babul, referring to their family backgrounds.
"Their (parents) are not speaking to the media, fearing their sons might be killed, leaving them in great torment."
He said his son had not changed his behaviour notably or become more religious before he went missing in December.
"It did not happen that all of a sudden he changed himself. He did not start going to the mosque suddenly," he said.
He noted that his son's room was not isolated but was near the rooms of the rest of his family.
"We often visited his room, but did not find any (religious) books. We did not see any souvenirs, magazines or related Islamic books," he said.
Mr Babul said of his son's participation in the attack: "It is very shameful for us - it's humiliating, disparaging and sad.
"It's painful and embarrassing. I am a forlorn father, a failed father. I seek pardon to all through you ... seek pardon to the nation."
The hostage siege was the worst recent militant attack in Bangladesh.
Previous killings were carried out by young men wielding cleavers and machetes and targeting atheists and other individuals accused of being enemies of Islam.
The escalation has raised global concerns about whether the South Asian country can cope with increasingly strident Islamist militants.
Bangladesh police have said they are investigating whether the attackers had links to the Islamic State group, which claimed responsibility.
However, the government has blamed domestic militant organizations bent on imposing Islamic rule.