After the blast, the Ahmedabad police on Thursday lodged an FIR and arrested three persons - two godown owners and their tenant who had stored chemical drums - on charges of culpable homicide.
The tenant who had stored drums filled with chemicals in the godown on Pirana-Piplaj Road on the city's outskirts was also arrested, an official said.
The explosion destroyed three to four adjoining godowns where labourers were packing textiles and garments, the police official said.
The explosion took place around 2:30 am in the factory at Dheku in Sajgaon industrial area of Khopoli town, located about 70 km from Mumbai.
During a nine-hour-long search and rescue operation, which ended around 8:30 pm, the city fire brigade pulled out 12 bodies and rescued nine persons from the rubble.
IOCL had awarded the contract to a Faridabad-based firm, Surya Shakti Vessels Pvt Ltd., to carry out the maintenance work of the LPG unit at Raj Bhavan square filling centre.
The incident took place at around 9 pm when a firecracker gift box, kept in a tiled roof house, exploded.
Ghazni province police spokesman Ahmad Khan Sirat said that a second roadside bomb killed two policemen, after it struck their vehicle that was making its way to the victims of the first explosion.
The Metropolitan Police said the two people killed in the explosion are yet to be formally identified but some local reports indicate that the victims may be of Indian-origin.
At least two floors of the building near Maskan Chowrangi in the Gulshan-e-Iqbal area in Karachi were severely damaged.
The Special Investigation Team, led by Crime Branch IG S Sreejit, which probed the mishap, filed the chargesheet in the Paravour Judicial First class magistrate court here.
The explosion apparently caused by a gas cylinder on Tuesday had ripped apart at least half a dozen neighbouring houses in Khatikaan locality under the Delhi Gate Police Station area.
The explosion that took place on October 7 had caused extensive damage to commercial and residential properties.
No one, however, sustained injury in the blast, which occurred on the second floor of the club on Beliaghata Main Road here around 5 am.
Meanwhile, IOCL officials have shared some documents with Commissionerate Police as part of the investigation.