Home Minister Asaduzzaman Khan Kamal said he hoped footage from the site would help identify the attackers.
Thirty-two closed-circuit cameras were installed at Hossaini Dalan area to bolster security during the Ashura.
Three explosions rocked a Shia gathering there on early Saturday killing one and injuring dozens.
Bangladesh’s Shia community takes out traditional procession from Hossaini Dalan’s Imambarha every year.
Police say they suspect the blasts were caught on surveillance cameras.
Imambarha management committee member Meer Zulfikar Ali said they had installed 16 security cameras several years ago and police installed another 16 three days ago.
“All the cameras are functioning properly,” he told.
The site of the attack was covered by security cameras, another member said.
Home Minister Kamal said two other unexploded bombs were found there.
The government says the attack was aimed at creating unrest while the ruling Awami League blamed the BNP and its allies for the blasts.
Attack on Shia community is unprecedented in Bangladesh.
Dhaka Metropolitan Police’s Joint Commissioner Krishnapada Roy said they had collected CCTV footage.
RAB has joined police in analysing them.
“It seems the attackers were at the procession,” he told. “It’s unlikely that the bombs were lobbed from outside.”
RAB’s Additional Director Ziaul Ahsan had told the bombers were inside the complex.
Several Shia families live in buildings on the north side of Hossaini Dalan.
A police officer said it was unlikely that the bombs were hurled from one of those buildings.
“But we’re not ruling it out,” the official added.