Muhammed Amin is beside himself with grief and despair.

His brother, Naveed Memon, was inside Gul Plaza when a massive fire ripped through the densely-packed shopping centre in Pakistan’s commercial capital, Karachi.

Like dozens of others, he still hasn’t been found.

“What should I tell my mother when I go home? What should I tell my nieces?” asks Amin.

“My nieces are crying for their father – they are asking me why he is late to come home. What should I tell them? How can I tell them that their father is gone?”

Housing an estimated 1,200 shops across a basement, mezzanine and three floors, Gul Plaza was a wholesale market that offered a wide range of cheaply-priced products, including wedding wear, toys, decorations, bed sheets, artificial flowers and baby clothes. The city’s residents would frequent it in droves, particularly ahead of festivals, weddings and other important occasions.

What started the fire is still unknown.

But witnesses say the speed at which it spread, a lack of working fire exits and the density of shoppers and stalls crammed into the building exacerbated the disaster.

Rehan Faisal, who owned a bedsheet shop, said that he was able to escape because his shop was located near one of the exits – he broke down the door to get out.

He said that although his staff had heard there was a fire in one part of the market, they had initially not worried because it was located some distance away from them.

“No-one knew it would spread so much,” Faisal added, saying it only took about “five to seven minutes” for everything to “burn before our eyes”.

Shoiab, 19, who worked at a decorations shop, said he first heard about the fire on a lower floor at around 22:00 local time (17:00 GMT) on Saturday night.

“Many customers and shopkeepers were coming up… and saying there was a fire downstairs. I was just beginning to comprehend the situation when the shop owner told me to lock up and get out,” he told BBC Urdu.

“Then suddenly everything was covered with smoke – we couldn’t see anything and there was panic and confusion everywhere. People were just running here and there. I knew some ways to get out of the plaza. But the first exit I tried was locked and the crowds were too dense for me to go the other way.”

With the facility due to close soon, most of the gates of the shopping centre were locked. Senior police official Syed Asad Raza told Reuters news agency that all but three of the centre’s 16 exits were locked.

Shoiab was among the luckier ones. He fainted amid the smoke, but someone – he doesn’t know who – pulled him out of the building to safety.

Another colleague who was trying to escape with him is still missing.

The confirmed death toll from the fire currently stands at 27, but more than 70 are still missing and the unstable structure of the still smouldering building is making it difficult for rescue officials to go inside and assess the full extent of the disaster.

Dr Abid Jalaluddin Sheikh, a senior rescue official, told BBC Urdu that rescue efforts were being slowed further because the structure of the building had been so severely damaged that it was at risk of completely collapsing at any time. He added that many bodies were unrecognisable and they would need to conduct forensic examinations to confirm the exact number of deaths.

Meanwhile crowds of people looking for their loved ones have gathered around the building, desperate for any news.

Muhammad Qaiser told the BBC that his wife, sister and daughter-in-law were among the missing. “They had said that they were going to the market. The last contact with them was at 20:00 when it was discovered that a fire had broken out. We do not know what happened to them.”

Qaiser said that officials were unable to help them, describing how his family had been told to visit both the burns centre and the morgue at different times.

Another resident, Haroon, said that three of his brothers had been inside the building. Two managed to escape but one was still missing.

“My brother called our parents from inside the plaza asking them to save him. He also called his friends and appealed to them, but no one could save him,” he said.

The survivor, Shoaib, is also still at the building hoping for news of his cousin, Faizan, who worked at a different shop.

“Every morning, I used to go to work and back with my cousin. Now I don’t feel like going back home without him. I’m waiting for him to be pulled out of the building alive,” he said, adding that his phone was ringing all the time because Faizan’s family keep asking if he had any news.

“I have no answers for them.”

As the searches continue, anger is growing.

On Monday, hundreds of protesters gathered around the building calling for accountability.

Karachi Mayor Murtaza Wahab, who arrived on the scene nearly 24 hours after the fire broke out, was met with jeers.

Muhammed Arif, whose nephew is among the missing, says that the relief work did not start on time and that “precious lives could have been saved”.

Many residents and politicians have echoed the sentiment that rescue officials took long to get to the building.

Faisal said that it took a long time for the fire brigade to arrive, “while the ambulances, which weren’t even needed at that moment – had already reached”.

News agency Reuters quoted rescue services as saying that authorities only received the first emergency call at 22:38 on Saturday, reporting that ground-floor shops were on fire. By the time firefighters arrived, the flames had already spread to the upper floors, engulfing much of the building.

Murad Ali Shah, the chief minister of the southern province of Sindh, which includes Karachi, has promised an investigation into the fire and response time.

And lawmakers from across the political spectrum on Tuesday condemned the fire and called for sweeping reforms in building safety, emergency response and urban governance, as the House debated an adjournment motion on the tragedy.

The prime minister is among those who have offered condolences and promised action.

But for those gathered at the ruins of Gul Plaza, this is little consolation.

“This is the third time in a while that a building has caught fire in the Saddar area of Karachi,” said Muhammed Arif.

“How long will this continue to happen and how many more people must die?”