Monday's explosion in the brown coal mine in Handlova, Central Slovakia, that killed 20 people, was probably caused by a wrong method of extinguishing decaying coal, the daily Pravda wrote on Friday, citing the investigators…The official investigation of the tragedy will take a longer time…An unnamed engineer from the mine said all people involved already know the cause of the accident… The company Hornonitrianske bane Prievidza, which owns the Handlova mine, has declined to comment on the causes of the accident before the investigation is closed.