A five-member team of crime scene unit, Criminal Investigation Department (CID), went to the Holey Artisan Bakery in Dhaka's Gulshan diplomatic zone to collect evidence, Bangla daily Prothom Alo reported, quoting Abul Hasan, inspector and a member of the team.
A bomb disposal unit of Detective Branch entered the restaurant premises at the same time, Hasan said.
Prime Minister Sheikh Hasina on Sunday said her government will find out "roots" of the gunmen, who attacked the restaurant.
"Describing the terror attack as unfortunate, the prime minister said, we must find out the roots of the culprits who supplied weapons and explosives to the terrorists for the barbaric attack," Ihsanul Karim, press secretary to Hasina told the media after she met Japan's State Minister of Foreign Affairs Seiji Kihara at her official residence.
Home Minister Asaduzzaman Khan said the jihadists who slaughtered 20 hostages were members of Jamaeytul Mujahdeen Bangladesh, a homegrown Bangladeshi militant outfit, and not followers of the Islamic State group.
Seven Japanese nationals were among the 20 hostages who were brutally murdered during the chilling siege before the commandoes stormed the popular hangout in Dhaka's diplomatic zone on Saturday morning.
Thirteen hostages were rescued while six of the gunmen, who attacked the upscale eatery on Friday night, were killed in the army-led operation.