The number of deaths from a fire in a mall in Pakistan's Karachi has risen to at least 50 as firefighters recovered more bodies from the debris of the charred building.

"We have found 20 to 25 dead bodies, or ‌you call them remains," Deputy Commissioner Javed Nabi Khoso told the media on Wednesday.

The Gul Plaza mall in Karachi — the country's biggest city — caught fire late on Saturday.

The blaze raged on for more than 24 hours before it could be extinguished.

But firefighters had to battle the flames once again until Tuesday after they reignited from the pile of ash and smouldering debris of the building.

Families give DNA samples

A rescue operation to search for the missing people trapped inside the multistory shopping complex was hindered by thick smoke that had spread through the mall as the fire burned, fire officials said.

Over 50 families have given DNA samples to help identify the victims, provincial health official Summaiya Syed told reporters outside the Civil Hospital Karachi mortuary.

"We will hand over the bodies to the family, once DNA samples are matched," she added.

A total of ‍84 people have been listed as missing, according to a state-run rescue service.

Authorities say most of the missing are feared dead, meaning the death toll could increase further.

Meanwhile, the relatives of the missing people have criticized the search-and-rescue effort as slow.

Investigation ordered in deadly Karachi fire

The cause of the fire is yet to be determined.

Authorities have launched a probe into the incident, with Pakistani media reporting that top officials of the inquiry committee visited the site on Wednesday.

The mall fire is the deadliest Karachi has seen in over a decade.

In 2012, over 260 people were killed in a blaze at a garments factory in the port city.

Edited by: Darko Janjevic