It was around 7:30 pm. Ali Noor was heading to his bookshop at least 100 metres off Rekha Neer, a three-storey building that is believed to be the site of the explosion. All of a sudden, he heard a loud bang that rocked the Moghbazar Wireless Gate area.
"I thought my eardrum was ruptured," said Ali as he was narrating his nerve-racking experience of the explosion.
He was shocked to see the extent of damage – chunks of concrete and shards of glass from broken windows littering the road, and wreckage of two buses in a hip outside the three-storey building.
At least 13 nearby buildings were also affected, with their glasses smashed.
There was an outlet of Shawrma House on the ground floor of the damaged building. "When the explosion took place, people inside the eatery were screaming in panic and some of them got injured with glass shards and heavy metal. They were trying to rush to safety," Ali said.
Inspector General of Police Benazir Ahmed confirmed that six people died in the blast. The deceased were bus driver Abul Kashem, college student Mostafizur Rahman, a law firm consultant Ruhul
Amin, British American Tobacco driver Mohammad Sawapan, a young woman Jannat Akter and her nine-month-old kid Sobhana.
A leak in Titas gas supply line might have caused the blast on Sunday evening, primary investigations found.
The Department of Explosives on Monday carried out a primary investigation at the blast site and found the presence of hydrocarbon at a risky level.
"We have detected the presence of 12% hydrocarbon. Some 4-18% of its presence is dangerous," said Abdul Hannan, deputy chief inspector of the Department of Explosives.
Titas Gas Transmission and Distribution Company Managing Director Ali Iqbal Md Nurullah, however, earlier claimed that they did not have any gas supply lines in the affected site of Moghbazar.
It was primarily suspected that an LPG cylinder blast might have caused the accident.
Titas officials also showed images of two LPG cylinders at the blast site.
But, the Department of Explosives said they did not find any gas cylinders at the site.
Meanwhile, the Fire Service and Civil Defence Department formed a five-member probe committee, headed by Director (operation and maintenance) Lieutenant Colonel Zillur Rahman.
Brig General Sazzad Hossain, director general of Fire Service and Civil Defence, on Sunday night told reporters that they found a gas line inside the building but they were yet to verify whether it was legal.
"We are taking this matter into account. The utility renovation project of that area may also have a link to the explosion," he added.
The DG also said the building was a risky one for years.
However, The Business Standard could not contact the building owner, Md Khokon, who went into hiding after the explosion. His mobile phone was found switched off.
Fire Service officials said over 70 injured underwent treatments at different hospitals, including 39 in Dhaka Medical College Hospital and 17 in Sheikh Hasina National Institute of Burn and Plastic Surgery.
Officials of Dhaka Community Medical College Hospital at Moghbazar said two of the injured died in the hospital and around 300 injured were treated there.
The victims were residents and workers of the affected building, customers of Shawrma House, pedestrians and passengers on vehicles.
Briefing reporters after visiting the spot on Monday morning, police chief Benazir said they were not suspecting the explosion to be a subversive act.
Police will start an investigation with the bomb disposal unit, he added.
Meanwhile, police formed a seven-member committee to investigate Sunday's explosion and assess damage.
The committee, headed by the Additional Commissioner of Dhaka Metropolitan Police's Counter-Terrorism and Transnational Crime (CTTC) unit, will also make recommendations to stop the recurrence of such incidents, according to an order of police headquarters.
However, a member of the committee, visiting the spot on Sunday night, told TBS that they did not find any gas cylinders at the spot.
"The explosion was very strong; we have analysed that a wave might have been generated and spread out within seconds, damaging buses and smashing glasses of nearby buildings," he added.
Firefighting officials hinted that the Moghbazar blast might be similar to the blast in the Narayanganj mosque last September, which killed at least 34 people.
"The blast in Narayanganj mosque was from a gas leakage. The one in Moghbazar has similarities with that," said Zillur.
Abul Kalam Azad, chief explosive inspector of the Department of Explosives, said a three-member probe body was formed with deputy chief explosive inspector as its chief and the committee would submit a report within seven working days.
He said they checked the site with a gas detector twice in the morning and evening and found the presence of gas at a risky level.
Meanwhile, the managing director of Titas Gas said they inspected the site and found no gas connection.