Faria Tasneem sensed trouble when her father did not answer her phone calls, despite several attempts to reach him.

Not picking up his daughter’s calls is unusual for Faisal Sarwar, who is a businessman in Bangladesh's Old Dhaka, parts of which lay in ruins after this week’s massive blaze.

As usual on a Wednesday evening, Faisal went to Churihatta Street of the neighborhood to spend a few hours with his friends.

At about 10.30 pm, he went to a pharmacy to buy some medicine with his friend Sheikh Mahmood just before a devastating fire broke out at the five-storey Haji Wahed Mansion on the other side of the street.

The fire started at 22.45 pm local time and rapidly spread to nearby buildings, leaving at least 67 people dead and more than 50 injured.

The authorities initially said 70 people had died, but fire service deputy director Dilip Kumar Das told EFE they have revised the figure to 67.

While Mahmood is in critical condition undergoing treatment in the Burns Unit of Dhaka Medical College Hospital, there is still no trace of Faisal.

"Normally my father never turns down my call,” a tearful Faria told EFE on Friday near the hospital morgue as she was waiting to provide authorities with her DNA sample.

"When we heard about the fire, I made him several calls, but no one answered. Then we all started looking for him in several hospitals. We checked the bodies in the morgue but could not identify him," she added.

Rumana Akter, a superintendent with the police’s Criminal Investigation Department, told reporters at the hospital that 21 victims out of 67 dead still remained unidentified.

"We collected samples like muscle, teeth and hair from all dead bodies yesterday. Today, so far, we took blood samples for DNA tests from 11 family members who claimed their dear ones were missing," she said.

"It will take us from 21 days to four weeks to complete the tests and identify the victims,” she added.

Humayun Kabir, however, was able to identify the body of his cousin Abu Bakar, 27, a businessman in Dhaka's Chawkbazar area, who had gone to a restaurant opposite Wahed Mansion just before the fire broke out.

"We identified his body yesterday and took it to our village for burial. But I am here to accompany my friend Aianus Hossain. His brother Haji Ismail is still missing," he said.

Teenage brothers Mohammad Raju and Mohammad Shakib appeared pale after giving blood samples to the hospital authorities. They were yet to identify the body of their father, Jafar Alam, 43.

Raju said his father went to Churihatta Street to buy plastic granules for his shop, but did not return home.

"I last spoke to him about 9.30pm (Wednesday). As he did not answer his phone, we came to the hospital. But he was also not here. We also checked over 30 dead bodies but could not identify him," said Raju.

Authorities said they were yet to identify the cause of the fire, but suspected that a gas cylinder blast might have triggered it.

"Perfume canisters stored in different floors expanded it. When we went up, we found the second floor was full of perfume canisters," Mehedi Ahmed Ansary, a member of probe committee formed by Dhaka City Corporation, told reporters.

Lieutenant Colonel Julfiker Rahman, a director of Bangladesh Fire Service and Civil Defence, said a canister for refilling gas lighters and perfume canisters acted like "bomb" during the fire.

"They all helped provoke the fire. Due to heat, these bottles came under extra pressure to act like a bomb... it happened due to chemicals. There is no way for fire to sustain so long with household materials," he said.

A resident of the neighborhood earlier said the Wahed Mansion building had a plastic granule shop on the ground floor, and a warehouse of perfume bottles on the first and a part of the second floor, while the other floors were residential apartments.

Many of the victims in the fire were bystanders as they could not escape the fast approaching flames owing to the narrow lanes of the neighborhood in Dhaka’s old city, one of the most densely populated areas in the world, with over 23,000 people living per square kilometer.

The area is a hub of chemical businesses and local perfume factories.

Authorities had banned the storage of chemical goods after a deadly fire in nearby Nimtoli area that killed at least 124 people in 2010.

By Azad Majumder