URGENT: Istanbul metro blast and injuries reported

Private Doğan news agency reported that a homemade cluster bomb has caused the blast and that a bomb disposal team has arrived at the scene of the explosion. Earlier news reports said the explosion may have been triggered by a power transformer. İstanbul Governor Vasip Şahin said in a statement that the cause of the blast is not yet known and that the authorities have been assessing all possibilities. Initial reports said the explosion was audible from several different parts of the city. Authorities have suspended services on the city's metro network, reports say. Source: BBC