A suspected gas explosion tore through a Bangladesh mosque killing at least 12 people while dozens suffered life -threatening burns , police said Saturday .
Worshippers were at Friday evening prayers when the blast sent a ball of flames through the mosque in the central district of Narayanganj , emergency services said .
Investigators suspected a spark from an air conditioner which came on after a power cut set off the gas .
“ Leaked gas entered the mosque , ” Narayanganj fire chief Abdullah Al Arefin told AFP .
“ When they shut the windows and doors and switched on the air conditioners there was an electricity spark that led to the explosion inside the mosque . ”