Fire that caused blackout probed

Authorities said Friday they are investigating what sparked a fire at a key substation that plunged 900,000 customers into darkness across Puerto Rico, with thousands still without power. Wayne Stensby, CEO of Luma Energy, which took over transmission and distribution this month for Puerto Rico’s 1.5 million electricity customers, said he expects power to be fully restored by late Friday. He said officials don’t know what caused a transformer to blow on Thursday evening in a secured area monitored by cameras. “We have not located the source of the fault,” he said. “It’s clear that the electrical system here in Puerto Rico is very fragile.”