Fire crews were called to a panel shop in Sunshine North after it was engulfed in flames about 4am on February 23.
Police believe the business was allegedly set alight before it spread to a factory on Marshall Street, where two people were sleeping at the time.
The two men, a 42-year-old and a 48-year-old both from Sunshine North, died at the scene.
Four warrants were executed by arson detectives yesterday at homes in Kurunjang and Melton South.
Police allege a gel blaster was seized from the Kurunjang address, while police located a sword, two machetes, two knives and a quantity of what appears to be cannabis at one of the Melton South addresses.
A 19-year-old Kurunjang man and an 18-year-old Melton South man have both been charged with two counts of arson causing death, three counts of criminal damage by fire and theft of motor vehicle.
Another 19-year-old Melton South man has been charged with assisting an offender (arson causing death) three counts of criminal damage by fire and weapons offences.
