The owner of a factory in Bangladesh where 52 people died in a fire was arrested on suspicion of murder on Saturday, along with seven other people.
This came as it emerged that children as young as 11 had been working at the site in Rupganj, an industrial town outside the capital Dhaka.
Police said Abul Hashem and four of his sons were among eight people detained over the inferno, which broke out Thursday and raged for more than a day.
A separate inquiry has been launched into the use of child labour at the food factory.
Jayedul Alam, police chief for Narayanganj district where the factory is located, said the entrance had been padlocked at the time of the blaze and that multiple safety regulations were breached.
“It was deliberate murder,” the police chief told AFP.
All eight people detained face murder charges.
Before his arrest, Mr Hashem told the Daily Star newspaper the fire “may have been a result of workers' carelessness”, suggesting that a discarded cigarette could have sparked the blaze.
Emergency services found 48 bodies on the third floor of the six-storey Hashem Food and Beverage factory, where noodles, fruit juice and sweets were produced.
The fire department said the exit door to the main staircase had been padlocked and highly flammable chemicals and plastics had been stored in the building.
Labour Minister Monnujan Sufian said inquiries had begun into the use of child workers at the factory.
Laizu Begum, who spent hours waiting outside the factory, said her 11-year-old nephew had been working on the third floor and was now missing.
“We heard the door of the floor where my nephew worked was padlocked. Then we realised, after seeing how big the fire was, that he is probably dead,” she said.
Outside the burnt shell of the factory and at the hospital morgue, AFP spoke to 30 survivors and relatives of the dead, who said child workers at the factory were paid 20 taka ($0.24) an hour.
Bilal Hossain, father of Mitu Akter, 14, who was among the missing, went to the Dhaka Medical College and Hospital morgue with a photo of his daughter, begging police and doctors to hand over her remains.
“I sent my baby girl to die,” said Mr Hossain. “How will I tell her mother?”
At the hospital, Chandu Mia held a photo of his 15-year-old daughter. “I am not sure if she is alive,” he said.
Ms Sufian said she had spoken to young survivors.
“I went to the hospital and I asked them how old they are. The youngest were 14,” she said.
Ms Sufian said some children aged as young as 14 were allowed to work in non-hazardous jobs, but that the Hashem factory was considered hazardous.
“If child labour is proved, we will take action against the owner and the inspectors,” she said.
Bangladesh pledged safety reforms after the Rana Plaza disaster in 2013, when a nine-storey complex collapsed, killing more than 1,100 people.
But there has been a series of fires and other disasters since then. In February 2019, at least 70 people died when a fire ripped through Dhaka apartments where chemicals were illegally stored.