By Ruma Paul and Zeba Siddiqui

DHAKA (Reuters) -At least 52 people were killed and 20 injured after a massive fire raged through a juice-making factory in Bangladesh, officials said on Friday, the latest industrial accident in a country with a track record of poor working conditions.

The fire started late Thursday on the ground floor of a six-story factory building in Narayanganj, southeast of Dhaka, and was still raging Friday evening as firefighters scrambled to control it.

Flames rose from the top floors of the building, where many workers had jumped out from to escape, as a key exit out of the working areas was locked, said fire official Abdullah Al Arefin.

“Three people died from jumping off the building to escape the fire and 49 charred bodies have been recovered,” Mustain Billah, the administrator for the Narayanganj district, told Reuters by phone from the scene.

“Firefighters are struggling to control it, as chemicals and flammable materials were stored inside the building,” he added.

The cause of the fire is not yet known, but police official Abdullah Al Mamun told reporters that three police teams have been dispatched to probe the incident and legal action would be taken against those responsible for the fire.

Dozens of disasters occur in Bangladesh each year due to poor fire and building safety standards. The latest incident is the worst since or August 2016, when more than 100 people fell ill in the southern Chittagong city after inhaling gas that leaked from a fertilizer factory.

Past accidents have mired the country’s robust textiles sector, which employs millions of people and contributes the most to Bangladesh’s economy.

Industry officials promised better safety standards after the 2013 collapse of the Rana Plaza garment factory building in Dhaka that killed more than 1,000 workers and injured hundreds. But many factories still fall short.

“We demand speedy trial and punishment of those responsible for this tragic murder incident through a fair investigation,” the nonprofit Bangladesh Legal Aid and Services Trust said in a statement. It also sought compensation for impacted workers and a probe into the cause of the fire, including reports of locked exits.

The factory is owned by the private firm Hashem Food and Beverage, a unit of Bangladesh’s multinational Sajeeb Group. Officials at both companies did not respond to calls and emails seeking comment on Friday.

Al Arefin said each building floor is about 35,000 square feet (3,250 square meters) but they were only accessible by two stairways, which many workers couldn’t get to as the fire had spread there. Some escaped to the roof from the stairs and were rescued, but many couldn’t, as a door leading to the roof was locked.

Dozens of family members protested outside the plant, demanding justice. But some, like Nazma Begum, were still looking for those lost. “There is no justice! Where is my son?” Begum cried out.

(Reporting by Ruma Paul and Zeba Siddiqui; Editing by Lincoln Feast and Christian Schmollinger)