Updated at 7.15pm
Two men were injured while servicing a generator at a showroom in Mrieħel on Thursday afternoon.
One of the men, a 27-year-old Maltese who lives in Tarxien, suffered grievous injuries while the other one, a 22-year-old French, refused medical care.
The police said the accident happened in Triq is-Sebħ at around 4pm.
They said the men were working on the roof when one of the generator's batteries blew up.
Both were taken to hospital by ambulance and fire engines were seen on site.
The police are investigating.