Islamabad, Pakistan (CNN) -- Police in the Pakistani city of Karachi have opened a murder case against the owner of a garment factory where a fire killed more than 250 people this week, a senior police official said Thursday.
Also under investigation are the two sons of the factory owner, whose name is Abdul Aziz; the managers of the factory; the shareholders of the factory; and any government official who failed to enforce safety regulations at the factory, said Amir Farooqi, a senior Karachi police official.
The announcement means police officers will investigate the fire -- one of the worst industrial accidents in Pakistan's history -- gather evidence and submit their findings to prosecutors who will then decide whether to charge the individuals.
Farooqi said police have opened a murder case because the exit doors of this factory were locked, preventing many people from escaping the blaze that swept through the building during Tuesday night and continued to burn Wednesday.
Nobody has been arrested in the case yet. Police officers are still looking for Aziz and his sons, who are believed to be "hiding," Farooqi said.
Other charges in the case may eventually include causing bodily harm, negligence and destruction of property, he added.
At this phase in the investigation, police do not have to name all of the accused. That's why they're not identifying any government officials or factory managers at this point.
Earlier Thursday, Karachi authorities lowered the death toll from the blaze to 258 from 289 previously.
The higher toll reported Wednesday became inaccurate because of the rapidly rising number of deaths and confusion amid multiple rescue and recovery operations, according to Karachi Fire Department Chief Ehtesham Salim and Shabih Saddiqi, a local government official.
Salim said the latest death toll is based on the number of bodies and remains recovered from the factory.
Several people are still missing and recovery crews are working to find them.
Salim said investigators are still trying to establish what caused the fire.
Journalist Nasir Habib contributed to this report.