Doctors yesterday collected hair and blood samples from the bodies of six “terrorists” to ascertain whether they had been under the influence of drugs while “carrying out” the attack on a Gulshan café.

The samples would soon be handed over to the US Federal Bureau of Investigation (FBI) for a test in their laboratory, said investigators and one of the doctors.

Sohel Mahmud, assistant professor of the forensic and medicine department at the Dhaka Medical College Hospital (DMCH), said they collected the samples on the request of the Counter Terrorism and Transnational Crime unit of the Dhaka Metropolitan Police.

The move came amid media reports that militants, especially members of the Islamic State, are popping addictive pills, which help “fuel their fury”, before attacking their victims.

The brutal way the attackers killed people at the Holey Artisan Bakery prompted investigators to suspect whether the terrorists had also taken similar drugs.

During a special meeting on terrorism and militancy at the Gono Bhaban on July 4, Prime Minister Sheikh Hasina too instructed to find out whether the attackers were on drugs.

A forensics team from the DMCH collected the samples from Dhaka's Combined Military Hospital where the bodies are kept.

The six dead include the café's pizza chef Saiful Islam who investigators say was one of the attackers. His family, however, said he was innocent.

Blood samples of the family members of the six men were also collected yesterday at the lab of the Criminal Investigation Department (CID) in the capital. 

Their DNA would be matched with those of the “attackers” to ascertain their relation, said a Detective Branch of police official, wishing not to be named. 

On July 1, terrorists stormed the Holey Artisan Bakery in the high security diplomatic zone in Gulshan, killing 20 hostages, mostly foreigners. Two police officials were also killed.