Bangladesh police arrested the owner of the factory where at least 52 people died in a fire late Thursday.
Abul Hashem, the owner of Hashem Foods, and four of his sons were among eight people detained on Saturday. Police say they all face murder charges.
Authorities said many of those who died were trapped inside the building because a main exit was locked.
Children were among the victims and a separate inquiry into the use of child labour has been launched.
Bangladesh labour minister Monnujan Sufian told AFP that she had been to a hospital and spoken to survivors as young as 14.
“If child labour is proved, we will take action against the owner and the inspectors,” she said.
Hashem Foods is a unit of the multinational Sajeeb Group of which Mr Hashem is chairman and managing director. Also arrested on Saturday was the group’s chief executive officer, Shahan Shah Azad, and other senior officials, the Dhaka Tribune reported.
Prior to his arrest, Mr Hashem told Bangladeshi media that “workers’ carelessness” such as a discarded cigarette could have started the fire.
The blaze broke out on Thursday night on the ground floor of the six-storey factory in Rupganj, an industrial town near the capital, Dhaka. Emergency crews said most of the victims had been trapped on the third floor.
Fire official Abdullah Al Arefin said each floor was accessible by two stairways which some workers couldn’t reach because the blaze had cut them off. He said some people managed to escape to the roof via the stairs and were rescued, but others could not because a door leading to the roof was locked. He said many of those trapped had jumped from windows to escape the flames.
The fire, fuelled by chemicals and plastics stored inside the building, burned for nearly 24 hours before it was put out.
Bangladesh is no stranger to deadly fires and disasters involving high-rise buildings and government critics say safety standards are still lax.